Acknowledging that he was "surprised and deeply humbled" by the news that he had won the Nobel Peace Prize, President Obama today urged the international community to work together on addressing the challenges of the 21st century.
"To be honest, I do not feel that I deserve to be in the company of so many of the transformative figures who've been honored by this prize," Obama said in brief remarks at the White House. "I do not view it as a recognition of my own accomplishments but rather as an affirmation of American leadership on behalf of aspirations held by people in all nations."
The president said the prize has been used as a means to provide momentum, but that no one person or one administration alone can solve all the problems.
"All nations must take responsibility for the world we seek," the president said. "We cannot tolerate a world in which nuclear weapons spread to more nations. ... We cannot accept the growing threat posed by climate change, which could forever danger the world we pass on to our children. ... We cannot allow the differences between people to allow the way we see one another."
Emphasizing the work he has done as commander in chief in pulling back forces from Iraq, Obama said that "some of the work confronting us will not be completed during our presidency" and that some work "may not be completed during my lifetime." But he added that he was hopeful the challenges will be met.
"This award is not simply about the efforts of my administration, it's about the courageous efforts of people around the world," he said.
Obama, only the third sitting U.S. president to win the prestigious award, will travel to Oslo in December to accept the prize in person. The White House says Obama will donate the full balance of the prize -- $1.4 million -- to charity but they did not say which charity, or charities, he has chosen.
The news that Obama was awarded the 2009 Nobel Peace Prize came as a surprise even to the White House. Press aides said they had heard from news reports weeks ago that the president had been nominated for a Nobel Peace Prize, but they do not believe Obama himself knew of his nomination.
The deadline for nominations is Feb. 1, meaning the president was nominated after being in office for just 11 days.
The award is "extraordinarily unprecedented," Michael Worek, author of "Nobel: A Century of Prize Winners," told ABC News.
"It would be like awarding the Oscar halfway through the movie. You're not saying it's a bad movie, you aren't knocking it. But we just don't know how it ends," Worek said.
Geir Lundestad, director of the Norwegian Nobel Institute, told "Good Morning America" the decision to pick Obama was unanimous.
"President Obama has changed very dramatically international politics," Lundestad told "GMA's" Diane Sawyer today. "We feel he has emphasized multilateral diplomacy, he has addressed international institutions, dialogue negotiations. He has inspired the world with his vision of a world without nuclear arms. He has changed the U.S. policy dramatically. There's a whole list."
Two key White House aides were both convinced they were being punked when they heard the news, reported ABC News' George Stephanopoulos.
"It's not April 1, is it?" one said.
Upon being called by ABC News at 5:45 this morning, a White House aide said, "This better be good."
When told by ABC News that the president had won the Nobel Peace Prize, the aide replied: "Oh, that is good."
The award comes as the president deals with a vast array of international challenges, from deciding whether to send more troops to Afghanistan, to how to deal with nuclear-ambitious Iran and North Korea.
Critics are sure to argue that Obama's accomplishments have yet to rival those of previous winners.
Lundestad admitted that the committee knew the world would be surprised by the decision and was aware that the president faces many major decisions ahead in Afghanistan, but added that the committee has made its choice and Obama has "nothing to fear."
"We knew the world would be positive, surprised and some would be stunned," Lundestad said. "We have discussed the situation in Afghanistan. We understand the foreign policy of the United States has to be a very complex one with many different considerations. But we point particularly to the overall approach."
The five-member Nobel Peace Prize committee, in announcing its decision, lauded the president for his work on climate change and international diplomacy.
"Only very rarely has a person, to the same extent as Obama, captured the world's attention and given his people hope for a better future," the chairman of the Norwegian Nobel Committee, Thorbjorn Jagland, said in a statement.
"His diplomacy is founded in the concept of those who are to lead the world must do so on the basis of values and attitude that are shared by the majority of the world's population. For 108 years the Nobel Committee has sought precisely the international policy and those attitudes for which Obama is now the world's leading spokesman. The committee endorses Obama's appeal that now is the time for all of us to take a share of responsibility for a global response for global challenges," the statement said.
Nobel Decision Stuns Many
When the announcement was made, even those in the room gasped in surprise.
Jagland found himself on the defensive, however, amid some criticism that Obama's work has yet to rival those of others who have won the award, considered an Olympic gold of international presidency.
"If you look at the history of the Nobel Peace Prize, we have on many occasions tried to enhance what many personalities is [are] trying to do," he said.
In his nearly nine months in office, Obama has had many firsts on the international stage -- he was the first U.S. president to address the United Nations General Assembly and the first to personally pitch a U.S. city to the International Olympic Committee. He also spoke at the G-20 meeting, pushed the international community to act on climate change, reached out to the Muslim world with a speech in Cairo in June and met with Israeli and Palestinian leaders in an attempt to accelerate the Middle East peace process.
But in terms of actual accomplishments, the list has yet to be filled, and it remains to be seen whether Obama's overtures to Iran and North Korea on nuclear weapons and to the Middle East have any bearing. His rhetoric on climate change has also been met with some resistance from India and China. In addition, Obama inherited two wars, and the growing violence in Afghanistan and Pakistan remains a key international challenge that the Obama administration still has to tackle.
Worek said throughout the history of the Nobel, the prize has been awarded for accomplishments and results, not for efforts the committee hopes one will make. He said he cannot think of any past precedent for when a prize was "rewarded for hope."
"This so far can only be rewarding efforts, because he hasn't had that much time to devote to results," Worek said.
Many analysts and politicians agree the award will likely ratchet up the pressure on Obama to do more on the international challenges facing him.
"I think all of us were surprised at ... the decision. But I ... think Americans are always pleased when their president is recognized by something on this order," Obama's former rival Sen. John McCain, R-Ariz., said in an interview with CNN's "State of the Union" that airs Sunday. "Nobel Committee, I can't divine all their intentions, but I think part of their decision-making was expectations. And I'm sure the president understands that he now has even more to live up to."
The award comes as a mixed blessing and is more about the promise the president brings rather than any concrete achievements. It presents the opportunity to further the dialogue with countries like Iran and North Korea, but it also turns up the pressure on Obama to present more results. Obama is the first U.S. president to win the prize in his first year in office.
The nomination process is kept secret, and it may be 50 years before the world finds out who nominated Obama.
Many U.S. presidents have been nominated for and been denied the Nobel Peace Prize, among them William Howard Taft, Warren G. Harding, Herbert Hoover, Franklin D. Roosevelt, Harry Truman and Dwight D. Eisenhower and foreign ministers Charles Hughes and John Foster Dulles.
The previous sitting U.S. presidents who won were Theodore Roosevelt in 1906 and Woodrow Wilson in 1919. Jimmy Carter won in 2002, after his presidency.
Asked on MSNBC this morning if the Nobel Prize was more a rejection of former President George W. Bush than an affirmation of Obama, White House senior adviser David Axelrod deferred judgment, saying he didn't have any knowledge of the politics or the thinking behind these decisions.
"I read the citation and I accept the citation for what it is," he said. "I think the president has worked hard to bring some issues to the floor internationally and to point the world in the direction of solving some very different problems and I think this is a recognition of that."
A spokesman for former President George W. Bush said his office would have no comment on the Nobel Prize.
Worek said the award to Obama could be a repudiation of the Bush administration, but the Nobel committee should not be giving out a Peace Prize "because you want to snub the other guy or say 'we're glad there's change.' For the Peace Prize, you really have to accomplish something."
In an ABC News/Washington Post poll, 57 percent of Americans approved of Obama's handling of international affairs, the Nobel committee's main concern.
Nobel Peace Prizes for political figures have not always reflected or engendered broad public support. In a Gallup poll in October 2007, fewer than half of Americans, 43 percent, said Al Gore deserved his Nobel.
In a Time/CNN poll in 1994, shortly before that year's announcement, Americans were divided on whether Jimmy Carter should receive a Nobel, 47-41 percent. They opposed it for Yitzhak Rabin, with 50 percent saying he should not get one; and opposed it more broadly for Yassir Arafat, with 64 percent saying he shouldn't receive it.
On the other hand, Gallup found a 67 percent approval of Mikhail Gorbachev's Nobel in 1990. And, in September 1997, it found that 63 percent favored one posthumously for Diana, princess of Wales, in recognition of her work to ban land mines. She wasn't named, but the International Campaign to Ban Land Mines won that year's Nobel Peace Prize.
World Reacts to Obama's Nobel
The Obama Nobel caused a ripple not just in the United States but around the world. Praise from international dignitaries poured in for Obama, but reaction -- especially on the Web -- ranged from confusion to anger to absolute shock. For many people, who thought Obama's unsuccessful efforts to bring the 2016 Olympic Games to Chicago was a sign of an international snub, the news was even more surprising.
International Atomic Energy Agency Director General Mohamed ElBaradei said he could not think of anyone more deserving of the honor.
"In less than a year in office, he has transformed the way we look at ourselves and the world we live in, and rekindled hope for a world at peace with itself," ElBaradei said in a statement. "President Obama has brought a new vision of a world based on human decency, fairness and freedom, which is an inspiration to us all."
German Chancellor Angela Merkel, who has met with Obama several times to discuss troops in Afghanistan, congratulated the president, calling the award "an incentive to the president and to all of us" to do more for peace.
"His advocacy for a nuclear-free world is a goal that we should all set for ourselves," Merkel said on a German TV station. "In a short amount of time, he has set a new tone for the rest of the world, bringing a willingness to negotiate and a readiness for dialogue and we should all support him in his efforts towards a world free of nuclear weapons."
Israel's President Shimon Peres perhaps offered the most gleaming praises for Obama.
"Very few leaders if at all were able to change the mood of the entire world in such a short while with such profound impact," Peres said in a congratulatory letter to Obama. "Under your leadership peace became a real and original agenda. And from Jerusalem, I am sure all the bells of engagement and understanding will ring again."
But on the ground, many people said the award was premature and that the U.S. president has a lot of work ahead of him. In Kenya -- the native country of Obama's father -- several people said they are happy Obama is in the White House but didn't think he has accomplished enough to be awarded a Nobel Prize. Two of the last six Nobel Peace prize winners have had Kenyan roots.
In Afghanistan and Pakistan, many assailed the Nobel committee for awarding the U.S. president the prize while a war rages in the region. Just today, a car bomb killed 41 and wounded hundreds in Peshawar, Pakistan.
Even in his home turf, the reaction was one of apprehension. The Republican National Committee assailed the decision of the Nobel committee.
"The real question Americans are asking is, 'What has President Obama actually accomplished?' It is unfortunate that the president's star power has outshined tireless advocates who have made real achievements working toward peace and human rights," Republican National Committee Chairman Michael Steele said in a statement. "One thing is certain -- President Obama won't be receiving any awards from Americans for job creation, fiscal responsibility, or backing up rhetoric with concrete action."
Conservative radio talk show host, Andy Parks, quipped that it's either April Fool's Day or he woke up still drunk.
"If the Republicans have any stones at all, they will immediately declare war on Norway," joked former Republican Iowa Rep. Fred Grandy, Parks' co-host of the morning show on WMAL-AM in Washington, D.C. "This is the silliest thing I've ever seen. This guy has done nothing. ... This is laughable."
Two members of the Center on International Cooperation at New York University even called on the president to decline the award "and ask that it be awarded to a more deserving beneficiary -- one whose contribution to peace is in the past, not the future."
ABC News' Rick Klein, Gary Langer, Karen Russo, Nick Schifrin and Steven Portnoy contributed to this report.