In Israel, Obama Vows to Prevent Nuclear Iran

Obama arrives in Israel and vows "unwavering commitment" to Israeli security.

JERUSALEM, March 20, 2013 — -- Seeking to reassure the United States's primary ally in the Middle East, President Obama today told Israeli Prime Minister Benjamin Netanyahu that his administration remains committed to doing "what is necessary" to prevent Iran from obtaining a nuclear weapon.

"We do not have a policy of containment when it comes to a nuclear Iran. Our policy is to prevent Iran from acquiring a nuclear weapon," Obama told reporters at a joint press conference after a series of closed-door meetings with Israeli leaders.

"The United States will continue to consult closely with Israel on next steps. And I will repeat, all options are on the table," he said.

It's no secret that Obama and Netanyahu have had a rocky relationship, although it was hard to tell by the way the two leaders publicly lauded each other and joked around.

During the American presidential campaign, Republicans alleged that President Obama was not committed to protecting Israel, but today Obama and "Bibi," as he called him, appeared at ease in front of the press.

Netanyahu even placed Obama's commitment to Israel's right of self-defense above that of any other U.S. president.

"I appreciate the fact that the president has reaffirmed, more than any other president, Israel's right and duty to defend itself, by itself, against any threat. We just heard those important words now. And I think that sums up our -- I would say, our common view," he said.

That does not mean there are not differences.

Netanyahu was firm in his belief that there must be a "credible threat of military action" to stop Iran's nuclear program.

The White House, however, continues to prefer to "resolve this diplomatically," according to Obama. "And there's still time to do so."

Israeli President Shimon Peres told ABC News' Jonathan Karl that there is no doubt in his mind that if there was a military strike against Iran, it would be led by the U.S.

When asked if a military strike would be necessary to stop Iran, Peres explained, "The one that can decide that and the one who has the capacity to implement it clearly, is the United States of America. Israel should not go alone when the United States is determined and clear on it."

Obama Pledges to Investigate Chemical Attack Allegations in Syria

On the escalating crisis in Syria, Obama said the U.S. is investigating an alleged chemical weapons attack, but that he remains "deeply skeptical" of President Bashar al-Assad's claim that rebels have used such weapons.

"The broader point is, is that once we establish the facts, I have made clear that the use of chemical weapons is a game changer," he said.

But Obama said he would seek to avoid unilateral U.S. action in Israel. Calls for an elevated American presence and potentially even the commitment of U.S. troops have grown, particularly from U.S. Senators Lindsey Graham and John McCain.

"I want to make sure that we're working as an international community to deal with this problem because I think it's a world problem, not simply a United States problem or an Israel problem or a Turkish problem," said Obama.

Obama Tells Israel "Our Alliance is Eternal"

Arriving here this morning for his first presidential visit to Israel, President Obama sought to reassure Israelis of the strong support from the U.S. as they face increasing threats in the region, declaring "our alliance is eternal."

Standing on the tarmac in Tel Aviv, Obama said it was "no accident" that he chose Israel for the first foreign trip of his second term.

"I see this visit as an opportunity to reaffirm the unbreakable bond between our nations, to restate America's unwavering commitment to Israel's security and to speak directly to the people of Israel and to your neighbors," Obama said.

"We stand together because we share a common story – patriots determined to be a free people in our land, pioneers who forged a nation, heroes who sacrificed to preserve our freedom, and immigrants from every corner of the world who renew constantly our diverse societies," he said.

White House officials have lowered expectations ahead of the president's trip, saying Obama will not present any new peace initiatives and expects no breakthroughs during his four-day stay in the region.

But it was clear the president was happy for some time outside the Washington beltway.

"It's good to get away from Congress," Obama said to Netanyahu in a candid moment captured by television cameras.

The president did not reference the Palestinians by name during his brief remarks, referring to them instead as Israel's "neighbors."

Obama's highly symbolic visit will consist largely of choreographed photo-ops and political tourism as Obama tries to win over the support of the Israeli people. The centerpiece of the trip will be the president's speech to the Israeli people Thursday.

The president has his work cut out for him. Polls here show Obama is still deeply unpopular with Israelis, and he's had a rocky relationship with Netanyahu.

Looming over the trip is the nuclear threat from Iran. Behind the scenes, Israel's new coalition government wants reassurance that the Obama administration will take out Iran's program if they cross the infamous "red line" and develop a nuclear weapon.

The U.S. and Israel don't see eye-to-eye on the timeline for taking action against Iran. Obama has said it would take Iran more than a year to develop such a weapon, but the Israelis believe they could develop one much sooner.

"As I begin this visit let me say as clearly as I can – the United States of America stands with the state of Israel because it is in our fundamental national security interest to stand with Israel," Obama said. "It makes us both stronger, it makes us both more prosperous, and it makes the world a better place."

Shortly after his arrival, Obama got a first-hand look at Israel's Iron Dome, the missile defense system funded by hundreds of millions of U.S. dollars. One of the system's batteries was brought to the airport so that Obama could see the U.S. investment up close.

Cameras caught a confused Obama asking where the tour of the missile system began. When a guide told him to follow the red line drawn on the tarmac, Obama joked, "Bibi is always talking to me about red lines. This is all a psychological ploy."

Related: Israeli President Shimon Peres Discusses Red Lines with ABC News' Jonathan Karl