On his first appearance at the 64th United Nations General Assembly, President Obama stressed international cooperation on climate change and called on developing countries to step up and do their part.
"Those rapidly growing developing nations that will produce nearly all the growth in global carbon emissions in the decades ahead must do their part as well. Some of these nations have already made great strides with the development and deployment of clean energy. Still, they will need to commit to strong measures at home and agree to stand behind those commitments just as the developed nations must stand behind their own," the president said at the U.N. Summit on Climate Change.
Touting the reforms his own administration has made to protect the climate, Obama called on developed nations, including the United States and China, to work together and assist others in taking similar steps.
"Difficulty is no excuse for complacency. Unease is no excuse for inaction. And we must not allow the perfect to become the enemy of progress," the president said. "Each of us must do what we can, when we can, to grow our economies without endangering our planet -- and we must all do it together."
Major Speech on World Stage
"For the international diplomatic audience, it's a major speech. I think for him personally, it will allow him to forget health care for four days," said Thomas Weiss, political science professor at the City University of New York and author of "What's Wrong With the United Nations and How to Fix It."
Later today, Obama will meet with Chinese President Hu Jintao. In addition to conveying an optimistic outlook on the economy -- China is the largest foreign holder of U.S. government debt -- Obama is also likely to bring up China's approach to climate change.
Climate has been a contentious issue for the Chinese government, which has increasingly been pressured by the international community to cut emissions and change its environmental policy.
The United Nations General Assembly: The World's Broadway Stage
The president this afternoon held what he called "frank and productive" meetings with Israeli Prime Minister Benjamin Netanyahu and Palestinian President Mahmoud Abbas at which he "was pretty tough" on both leaders, conveying "a sense of his impatience and seriousness and his analysis that they need to get going," a senior White House official said.
The White House official, who spoke on condition of anonymity because of the sensitivity of the talks, said Obama conveyed a sense that a Mideast peace process "can't just be a perpetual kabuki" if he is "going to continue to invest his political capital."
Before the meeting with the two leaders, Obama said, "Despite all the obstacles, despite all the history, despite all the mistrust, we have to find a way forward. We have to summon the will to break the deadlock that has trapped generations of Israelis and Palestinians in an endless cycle of conflict and suffering."
As it was for his predecessors, the Middle East peace process is a thorny issue for Obama. The president has consistently pushed for a two-state solution. While it has thrown its support behind Israel, the Obama administration has insisted that the government stop building settlements and he said today that "they need to translate these discussions into real action on this and other issues."
The president added that Palestinians have strengthened their efforts on security but "need to do more to stop incitement and to move forward with negotiations."
The senior White House official said that the Israelis "said they're ready to go" with talks, "though in the run-up to today they were a little balky."
There was some push-back from both Abbas and Netanyahu.
Afghanistan Dominates Discussions
Amid a controversy over sending more troops to Afghanistan, the president on Wednesday will host a special event for world leaders contributing the most troops and police to the U.N. effort in that country, including Bangladesh, Ethiopia, Ghana, Italy, Pakistan, Rwanda and Uruguay.
"The expectations of the president domestically as well as internationally are almost off the charts," Weiss told ABC News. "He will be received with some skepticism but also with much warmth."
The president has yet make up his mind about the strategy for Afghanistan. Gen. Stanley McChrystal is expected to request additional troops for the war-torn country, but administration officials have said Obama wants to fully assess the situation and strategy before committing additional forces.
"The country is weary of the war,'' Obama said on "The Late Show With David Letterman" Monday. "What I'm trying to do at this point is to make sure that ... we have got a coherent strategy that can work."
"I've got to make sure that the policy in place was worthy of their sacrifice. That's something that we're going to work through systematically."
World Leaders to Avoid
On Wednesday, the president will speak to the United Nations about his desire for a new direction for international relations, and on Thursday, he is scheduled to chair a U.N. Security Council meeting on nuclear nonproliferation.
As the world's leaders congregate in New York, there are some leaders from whom Obama's aides will likely try to keep the president at a distance, namely Iran's President Mahmoud Ahmadinejad.
"With respect to the Iranian leader, I don't think there's much likelihood that there will be an interaction. There's no obvious venue in which that would occur, and certainly, we have no meetings or anything of the sort planned," Susan Rice, U.S. ambassador to the United Nations, told reporters Friday.
Other leaders the president will likely want to avoid: Venezuelan President Hugo Chavez and Libyan leader Moammar Qaddafi.
In July, Qadaffi approached Obama at the summit in L'Aquila, Italy, and the image of the two shaking hands caused an uproar in some quarters of the United States.
And in April, Chavez dramatically gave the president a book critical of the role of the United States in Latin America. Critics, then too, lashed out at the president for accepting the book and shaking hands with Chavez.
Aides also do not want critics harping on whether or not Obama bowed before Saudi King Abdullah in April, even if President Bush got more intimate with the leader of the oil-rich nation during his presidency.
"This really is the world's Broadway stage No. 1. It is really made for a theater worldwide," said Weiss.
Nor do aides want America's opponents embarrassing the American leader on his own turf, actions that at times make for favorable press back home. In 1960, at the same venue, Soviet Union leader Nikita Khrushchev banged his shoe on the table in anger. At the General Assembly meeting in 1974, Palestinian leader Yasir Arafat wore a holster, telling delegates he had come "bearing an olive branch and a freedom fighter's gun."
At the General Assembly in 2006, Chavez insulted then-President George W. Bush.
"The devil came here yesterday," Chavez said then, referring to Bush. "And it smells of sulfur still today."
The world will be closely watching Obama as he delivers his first performance on this world stage.
ABC News' Kristina Wong contributed to this report.