Pres. Obama met with Israel's Prime Minister Netanyahu at the White House Monday. (Pablo Martinez Monsivais/AP …President Barack Obama and Israeli Prime Minister Benjamin Netanyahu held one of their more studiously cordial meetings at the White House Monday. But the concerted effort to project a united front--after many previous prickly encounters--did little to mask the fact that there are genuine differences and tensions in the allies' views on how to deal with the Iran nuclear program and in what time-frame, analysts said.

"Both the prime minister and I prefer to solve this diplomatically," Obama said at the top of his three-hour meeting with the Israeli leader, echoing the thrust of his comments to the pro-Israel lobby group the American Israel Public Affairs committee (AIPAC) Sunday. The administration has continued to push diplomacy as the key to getting Iran to agree to curb its nuclear program.

"Ultimately Iran has to make the decision to move in that direction," Obama said, adding that if that fails, however, "When I say all options are on the table, I mean it."

"Israel and America stand together," Netanyahu said Monday. But Israel reserves the right to defend itself, he asserted: Israel is "the master of its fate," he said.

"Really it's in the interest of both Netanyahu and Obama to try to put some of the past tension behind them," Haim Malka, a Middle East analyst at the Center for Strategic Studies told Yahoo News in an interview Monday. "And I think on the PR-front the atmospherics have been good."

"Obama, in his speech to AIPAC, made a strong case for his ongoing commitment to Israel's security; but at same time he was clear about maintaining his own position and not getting locked into Netanyahu's red lines," Malka continued. "I think Netanyahu came here with the clear objective to move the president on the red lines and on the timeline."

But Obama held his ground, Malka noted. "The president said very clearly —he thinks there's a chance for a diplomatic route," he said.

"In essence, [Obama's statements] are a mix of reassurance ('We've got this') and dissuasion ('Don't do this')," Colin Kahl, former deputy assistant secretary of defense for the Middle East in the Obama administration, told Yahoo News by email Monday

American and Israeli leaders publicly agree that Iran will not be permitted to get a nuclear weapon—if need be, both say they will resort to military force to destroy Iran's known enrichment and ballistic missile facilities. But they disagree about whether diplomacy or force would do more to set back Iran's nuclear effort, and how much time there is to act.

"The U.S. takes the attitude that we want to permanently solve the problem of the Iran nuclear program," Patrick Clawson, deputy director of research at the Washington Institute for Near East Policy, told Yahoo News in an interview. "And the only way to [permanently solve the problem] is to persuade the Iranians to come to an agreement."

Obama and Netanyahu disagree however about the virtue of further negotiations with Iran.

Netanyahu "truly believes that negotiations with Iran will merely lead to stalling and delaying tactics and cover for continuation of their work on their nuclear program," a Washington Middle East expert said on condition of anonymity.

Netanyahu has called publicly for a complete halt to Iranian enrichment before any new negotiations with Iran are undertaken--a condition the United States seems unlikely to accept.

But the United States is also devising a confidence-building measure to test whether the Iranians are serious about returning to international nuclear talks, Clawson noted. Under the proposed confidence-building measure that American diplomats have been quietly discussing with international partners, Iran would be asked agree to halt its 20 percent enrichment in exchange for a suspension of new UN Security Council sanctions. (Some Iran experts say Iran may also be asked to send out its stockpile of 20 percent enriched uranium in exchange for support for a Tehran reactor that produces isotopes used to treat Iranian cancer patients.)

The confidence-building measure is a small step that can help reduce the tremendous mistrust between Iran and the international community, while helping put "time back on the clock" for possible negotiations to a long term deal, Clawson explained.

At a crucial time in the standoff over Iran's suspect nuclear weapon, President Obama is sending his national security adviser to Israel from February 18-20 to discuss that tense showdown as well as the bloody crackdown in Syria, the White House announced Friday.

Tom Donilon will meet with senior Israeli officials to discuss "a range of issues, including Iran, Syria," the White House said in a statement.

The statement also noted that Donilon's visit "is the latest in a series of regular, high-level consultations between the United States and Israel, consistent with our strong bilateral partnership, and part of our unshakable commitment to Israel's security,"

News of the trip comes as the United States and its allies are weighing the impact of economic sanctions on Iran as well as Tehran's offer, in a letter to the European Union, to resume negotiations over its nuclear program. There is also talk in US and other media that Israeli patience may be running out and that some kind of military action could be months, or less, away.

"We remain willing to engage in talks with the Iranians so long as they have a constructive approach to those negotiations, and that means a constructive approach that understands that the purpose is for Iran to live up to its international obligations and to abandon its nuclear weapons ambitions," Obama spokesman Jay Carney told reporters aboard Air Force One on Friday.

Tehran denies seeking nuclear weapons and says its atomic program aims to produce energy for civilian purposes, but Iranian leaders have recently acknowledged that several new rounds of sanctions are hurting the Islamic republic's economy.

"The sanctions have had a positive — well, they've had a harmful effect on the Iranian economy, a disruptive effect on the Iranian regime, and that was the intention," said Carney.

"We will continue to pressure an isolate Iran unless and until it changes its behavior," he said.