President Obama reaffirmed his staunch commitment to Israel on Sunday, making clear in no uncertain terms that “I have Israel’s back.” But, at the same time, he urged Israel and its supporters to allow time for diplomacy and “crippling” sanctions on Iran to take hold to halt Tehran’s nuclear program.

Addressing the American Israel Public Affairs Committee, the influential pro-Israel lobby group, Obama tried to reassure the crowd of 13,000 people, who initially greeted him with a lukewarm response, by saying that if Iran fails to meet its obligations and the problem remains, “we must accomplish our objective.”

{mosads}“Iran’s leaders should know that I do not have a policy of containment, I have a policy to prevent Iran from obtaining a nuclear weapon,” Obama said, drawing hearty applause from the crowd. “And as I’ve made clear time and again during the course of my presidency, I will not hesitate to use force when it is necessary to defend the United States and its interests.”

During his address, which comes one day before he sits down with Israeli Prime Minister Benjamin Netanyahu, Obama sought time and again to reassure Israel and its supporters that he will do whatever it takes to help defend the country.

“Over the last three years, as President of the United States, I have kept my commitments to the state of Israel,” Obama said. “At every crucial juncture, at every fork in the road, we have been there for Israel. Every single time.”

The president added that “whenever an effort is made to delegitimize the state of Israel,” his administration has opposed it.  

”We will do what it takes to preserve Israel’s qualitative military edge — because Israel must always have the ability to defend itself, by itself, against any threat,” Obama added.

The president has faced criticism from GOP lawmakers concerned his 2013 budget proposal fails to devote enough aid to Israel in light of the threat from Iran.

“There should not be a shred of doubt by now: when the chips are down, I have Israel’s back,” he said.

At the same time, Obama called for patience, saying that as commander in chief, he has a “deeply held preference” for peace over war.

“I have sent men and women into harm’s way. I have seen the consequences of those decisions in the eyes of those I meet who have come back gravely wounded, and the absence of those who don’t make it home. Long after I leave this office, I will remember those moments as the most searing of my presidency,” he said. “For this reason, as part of my solemn obligation to the American people, I only use force when the time and circumstances demand it.”

Republicans though have been critical about Obama’s approach with Iran, attempting to find a weakness in his foreign policy track record, which has been bolstered by the killing of terrorist Osama bin Laden. 

On Sunday, before Obama’s speech began, the Republican National Committee slammed the president, sending an email to reporters with the subject line: “Another AIPAC, Another reminder of Broken Promises.”

GOP presidential candidates have accused Obama of weakening the U.S. relationship with Israel.

“If Barack Obama gets reelected, Iran will have a nuclear weapon, and the world will change if that’s the case,” Mitt Romney said in Georgia, following Obama’s speech. 

Romney said Obama had “failed to put into place crippling sanctions against Iran.”

“He’s also failed to communicate that military options are on the table and in fact in our hand. And that it’s unacceptable to America for Iran to have a nuclear weapon,” he said. “I will have those military options, I will take those crippling sanctions and put them into place, and I will speak out to the Iranian people of the peril of them becoming nuclear. It’s pretty straight-forward, in my view.”

On Sunday, appearing on CNN’s “State of the Union,” GOP presidential candidate Newt Gingrich said he doubts Obama’s commitment to Israel.

“I mean, we’re being played for fools,” Gingrich said. “You have every evidence that this administration is desperately trying to get the Israelis not to preempt and, frankly, an Israeli prime minister faced with the threat of nuclear arms in Iran is going to preempt.”

GOP presidential candidate Rick Santorum said recently that the U.S is “throwing Israel under the bus.”

“We’re going to say, ‘Oh, Iran, we don’t want you to get a nuclear weapon — wink, wink, nod, nod — go ahead, just give us your oil.’ Folks, the president of the United States is selling the economic security of the United States down the river right now,” Santorum said during a speech in Oklahoma City last month.

Appearing at the AIPAC conference in a roundtable, Liz Cheney, the daughter of former Vice President Cheney, drew big applause from the audience after she said that the Obama administration has done more to “delegitimize” and undermine Israel.

Obama railed against his critics in his speech on Sunday, reminding the crowd that “during this political season, [when] you hear some question my administration’s support for Israel, remember that it’s not backed up by the facts.”

“And remember that the U.S.-Israel relationship is simply too important to be distorted by partisan politics,” he continued. “America’s national security is too important. Israel’s security is too important.”

At the conference, Israeli President Shimon Peres, who spoke on Sunday, thanked Obama “for being such a good friend.” 

In his speech, Peres said Obama will “never permit Iran to become nuclear.”

“Dear friends, the United States and Israel share the same goal of preventing Iran from developing a nuclear weapon,” Peres said. “I know your commitment to Israel is deep and profound.”

After Obama wrapped up his speech, he spent more than 30 minutes talking to Peres backstage, a White House official said, adding that it was not a formal bilateral meeting. Obama also congratulated Peres on the Medal of Freedom, which he will present to the Israeli leader this summer.

On Sunday, before a meeting with Jewish leaders in Ottawa, Netanyahu said he “very much appreciated” that Obama “reiterated his position that Iran must not be allowed to develop nuclear weapons and that all options are on the table.”

“I also appreciated the fact that he made clear that when it comes to a nuclear armed Iran, containment is simply not an option, and equally in my judgment, perhaps most important of all, I appreciated the fact that he said that Israel must be able to defend itself, by itself, against any threat,” Netanyahu said. 

“I appreciate all his statements and I look forward to discussing them further with President Obama tomorrow.”

Netanyahu’s government has said time is running out for a military strike against Iran that would prevent the Islamic republic from developing nuclear weapons, something Israel sees as an existential threat.

The two leaders are said to have a tense relationship. The last time they sat down together at the White House, in July, Netanyahu appeared to lecture Obama on the history of Israel before a gaggle of television cameras.

But in an interview with The Atlantic last week, Obama called their relationship “functional,” and if nothing else brutally honest.

“I actually think the relationship is very functional, and the proof of the pudding is in the eating,” Obama said in the interview. “The fact of the matter is, we’ve gotten a lot of business done with Israel over the last three years. I think the prime minister — and certainly the defense minister —would acknowledge that we’ve never had closer military and intelligence cooperation.”

In the days leading up to the AIPAC conference, Obama sought to make his position on Iran clear.

In the Atlantic interview, Obama tried to reassure Israel, putting forth an “I say what I mean” attitude, while sending a warning to both Iran and Israel.

“I think that the Israeli government recognizes that, as president of the United States, I don’t bluff,” Obama said. “I also don’t, as a matter of sound policy, go around advertising exactly what our intentions are. But I think both the Iranian and the Israeli governments recognize that when the United States says it is unacceptable for Iran to have a nuclear weapon, we mean what we say.”

Reaction to the president’s speech was mixed. Some attendees said Obama struck the right tone, explaining exactly where he stands on Iran and making his commitment to Israel well-known. “He needed to hit this right,” said one attendee who is actively involved in U.S.-Israel relations.

On Sunday, AIPAC’s spokesman Patrick Dorton said in a statement: “We welcome the president’s remarks and his strong resolve to work with Israel to solve the Iranian challenge.”

Outside the conference, which took place at the Washington Convention Center, about 100 demonstrators protested various causes. Some held signs reading “Stop funding Israel terror. “No War on Iran,” read another.

—This story was posted at 12:31 p.m. and has been updated.