President Obama said Monday that Iran must agree to freeze its nuclear activity for at least a decade in order to close a deal with the U.S., as his administration made its case for ongoing negotiations while Israeli Prime Minister Benjamin Netanyahu warned that the talks had put the world in danger.

Obama acknowledged that the odds of reaching such a deal weren't good and that only if other countries were able to verify that Iran was keeping its word would a deal be plausible.

“There’s no other steps we can take that would give us such assurance that they don’t have a nuclear weapon,” Obama said in an interview with the Reuters news service.

His comments came hours after Netanyahu, opening a controversial and diplomatically fraught visit to Washington, drew loud cheers from thousands of supporters of Israel during his first public stop. Republican House Speaker John A. Boehner of Ohio invited Netanyahu to Washington weeks ago without telling the White House until the plans were final, and the Israeli leader is to address lawmakers Tuesday.

“The purpose of my address to Congress tomorrow is to speak up about a potential deal with Iran that could threaten the survival of Israel,” Netanyahu said at a meeting of the American Israel Public Affairs Committee, as he displayed a graphic showing terrorist operations that he said Iran backed around the world.

“This is what Iran is doing now without nuclear weapons. Imagine what Iran would do with nuclear weapons,” he said.

Netanyahu insisted that his visit was “not intended to show any disrespect to President Obama" or his office. "I have great respect for both," he said.

The speech is "also not intended" to inject Israel into "the American partisan debate," he added.

Obama said that the disagreement with Netanyahu over his decision to speak to Congress this week is simply a distraction and that it would not be “permanently destructive” to relations between the U.S. and Israel.

"This is not a personal issue,” Obama said. “I think that it is important for every country in its relationship with the United States to recognize that the U.S. has a process of making policy.”

Still, he acknowledged that there is “substantial disagreement” between his administration and the Netanyahu government over how to keep Iran from moving forward with its nuclear progam.

But the very fact that the Israeli leader felt the need to publicly explain his visit underscored the extraordinary political and diplomatic nature of his visit -- that of a foreign leader coming to Washington to openly campaign against the U.S. government's foreign policy.

Netanyahu, however, declared that he had a “moral obligation to speak up in the face of these dangers” from Iran “while there is still time to avert them.”

“For 2,000 years my people, the Jewish people, were stateless, defenseless, voiceless,” he said. “We were utterly powerless against our enemies who swore to destroy us.” Now, he said, Israelis have a voice. “I plan to use that voice.”

At the same time, he sought to rebut critics in the U.S. and in Israel who say his highly public campaign against the Obama administration’s Iran diplomacy has undermined the U.S.-Israeli relationship.

“Disagreements in the family are always uncomfortable,” he said. “But we always must remember we are family. Our alliance is sound. Our friendship is strong. “

Even so, Obama said Netanyahu’s doomsday predictions about nuclear talks with Iran have not come to pass.

"Netanyahu made all sorts of claims: This was going to be a terrible deal. This was going to result in Iran getting $50 billion worth of relief. Iran would not abide by the agreement. None of that has come true,” Obama said.

In fact, he said, "during this period we’ve seen Iran not advance its program. In many ways, it has rolled back elements."

Netanyahu was preceded by Samantha Power, the U.S. ambassador to the United Nations, who said the political dispute should not cloud the goals the U.S. and Israel share.

“The United States of America will not allow Iran to obtain a nuclear weapon, period,” Power said. She said the diplomatic talks with Iran are “aimed centrally at denying Iran a nuclear weapon.”

“The U.S. will take whatever steps are necessary to protect our national security and that of our closest allies,” Power said. “We believe diplomacy is the preferred route.”

The tension between Netanyahu and the administration is unsettling to many members of AIPAC, a group that, while hawkish, also has deep ties with Democrats. Some who sympathize with Netanyahu’s position said he might have gotten better traction with a different approach.

“I regret that the way the invitation played out puts the spotlight on partisan issues,” said Rob Ruby, 65, a retired attorney from Piedmont, Calif. “Speaker Boehner, whether he did it intentionally or not, appears to be trying to create a wedge issue out of Israel.”

Braxton Marcela, a law student at American University, said that while he had doubts about the negotiations with Iran, he sees no reason for the end run around the White House.

“None of us knows how things might have played out if protocol had been followed,” he said.

Linda Lippitt was among the several unyielding supporters of Netanyahu in the crowd who said a nuclear Iran presents a kind of existential threat to Jews not faced since World War II.

“This Iranian issue is perhaps even more of a peril than the Nazis were to the world,” said Lippitt, a 72-year-old developmental pediatrician from Atlanta. “Look at what Iran has done to destabilize the Middle East without a nuclear weapon.”

Staff writer Christi Parsons contributed to this report. For more on policy and politics, follow @DavidLauter on Twitter.

UPDATES:

3:14 p.m.: This article has been updated with comments from President Obama.

9:22 a.m.: This article has been updated with reaction from the AIPAC audience.

7:58 a.m.: This article has been updated with live remarks from the speech.

7:30 a.m.: This article has been updated with live remarks from the speech.

7:36 a.m.: This article has been updated with Netanyahu's warning about the effects of an Iran deal.