WASHINGTON >> In a display of unity between allies who often disagree, President Barack Obama assured Israel’s visiting leader Monday that the United States "will always have Israel’s back," and said the U.S. and Israel agree that diplomacy is the best way to resolve the crisis over potential Iranian nuclear weapons.

"Both the prime minister and I prefer to solve this diplomatically," Obama said as he and Israeli Prime Minister Benjamin Netanyahu began several hours of White House consultations. The U.S. will consider all options in confronting what it sees as the unacceptable outcome of an Iranian bomb, Obama said.

"Israel and America stand together," Netanyahu said. He added that Israel is a sovereign nation with the right to defend itself, a pointed reference to the main question hanging over Monday’s high-stakes meeting: Whether to try to stop an Iranian bomb by with a military attack in the next several months.

Israel must remain "the master of its fate," Netanyahu said.

Obama will try to persuade Netanyahu to slow quickening pressure among many in his hawkish government to attack Iran’s disputed nuclear development sites. Obama is trying to avert an Israeli strike that could come this spring, and which the United States sees as dangerously premature.

The president is expected to tell Netanyahu in private at the White House that although the U.S. is committed to Israel’s security it does not want to be dragged into another war. Obama is unlikely to spell out U.S. "red lines" that would trigger a military response, despite Israeli pressure to do so.

Obama previewed the Oval Office meeting with a speech Sunday to American supporters of Israel, a key constituency in this election year.

Obama said he doesn’t want war but insists he would attack Iran if that was the only option left to stop that nation from getting a nuclear weapon.

"Loose talk of war" only plays into Iran’s hands, Obama said.

U.S. officials believe that while Tehran has the capability to build a nuclear weapon, it has not yet decided to do so. They want to give sanctions time to pressure Iran to give up any military nuclear ambitions. Israel says the threat is too great to wait and many officials there are advocating a pre-emptive strike.

Obama did not directly call on Israel to stand down, and made a point of saying Israel should always have the right to defend itself as it sees fit.

That was the part of Obama’s speech to the American Israel Public Affairs Committee that Netanyahu said he liked best. Speaking to reporters in Canada ahead of his arrival in the U.S., Netanyahu made no reference to the sanctions and diplomacy Obama emphasized.

Obama is unlikely to persuade Netanyahu that economic sanctions and diplomacy are enough to prevent Iran from getting a nuclear weapon, and he is unlikely to win any new concessions from Netanyahu on peace talks, the issue that drew bad blood between the two men in previous meetings and led the Israeli leader to publicly scold Obama last year.

Netanyahu has not publicly backed a military strike, but his government spurned arguments from top U.S. national security leaders that a preemptive attack would fail.

"Now is not the time for bluster," Obama said. "Now is the time to let our increased pressure sink in."

Israeli President Shimon Peres, who had a meeting with Obama Sunday, said he "came out with the feeling that the man is determined to prevent Iran from attaining nuclear weapons."

Netanyahu was more subdued in reacting to Obama’s comments Sunday, saying, "more than everything, I value his statement that Israel must be able to protect itself from all threats."

Obama framed military force as a last resort, not the next option at a time when sanctions are squeezing Iran. He said just the talk of war has driven up the price of oil to the benefit of Iran.

Although Israel says it hasn’t decided whether to strike, it has signaled readiness to do so within the next several months. The top U.S. military officer recently called a unilateral strike "imprudent," a mild catchall for the chain-reaction of oil price hikes, Iranian retaliation, terror strikes and a possible wider Mideast war that U.S. officials fear could flow from an Israeli strike.

Israel says a nuclear-armed Iran would be a threat to its existence. It cites Iranian leaders’ repeated calls for Israel’s destruction, support for anti-Israel militant groups and its arsenal of ballistic missiles that are already capable of striking Israel. Israel also fears a nuclear Iran would touch off an atomic weapons race in a region hostile to Israel’s existence.

Addressing the powerful pro-Israel lobby, Obama delivered messages to multiple political audiences: Israel, Iran, Jewish voters, a restless Congress, a wary international community and three Republican presidential contenders who will speak to the same group Tuesday.

At the core was his assertion that the United States will never settle for containing a nuclear-armed Iran or fail to defend Israel.

The head of the U.N. nuclear agency said Monday his organization has "serious concerns" that Iran may be hiding secret atomic weapons work, as he acknowledged failure in his latest attempt to probe such suspicions and listed recent atomic advances by Iran.

"The agency continues to have serious concerns regarding possible military dimensions to Iran’s nuclear program," International Atomic Energy Agency chief Yukiya Amano said in Vienna.