Israeli Prime Minister Benjamin Netanyahu has told US President Barack Obama that Israel must always remain "master of its fate".

Meeting the Israeli leader at the White House, Mr Obama said a nuclear Iran would be an "unacceptable" development.

On Sunday, Mr Obama told a pro-Israel conference in Washington there had been too much "loose talk" of war with Iran.

Israel fears Iran is seeking to develop nuclear weapons, although Tehran insists its nuclear plans are peaceful.

"The bond between our two countries is unbreakable," Mr Obama said, as the two leaders sat side-by-side in the Oval Office.

Analysis There was no war plan, no timetable for military action. But this was still fighting talk. In foreboding terms, Benjamin Netanyahu spelt out the dangers of a nuclear-armed Iran, and left little doubt that he will do everything possible to stop it becoming a reality on his watch. A pointed reference to America's refusal to bomb Auschwitz in 1944 was an implicit challenge to the Obama White House to act now. Washington agrees with the objective of denying Iran nuclear weapons, but this visit has exposed a fault line on strategy. The Americans believe sanctions are slowly biting, and that hasty military action carries too many risks. But Mr Netanyahu could barely conceal his contempt for sanctions, and argued that the bigger risk lies in NOT acting soon. Moving forward, the two leaders have pledged to "consult closely." These are wary allies, short on trust - but both aware that this is a vital relationship at a critical time.

The president emphasised: "We believe there is still a window that allows for a diplomatic resolution," but added that the US would consider "all options" in dealing with Iran.

"I know that both the prime minister and I prefer to resolve this diplomatically," Mr Obama said. "We understand the costs of any military action."

For his part, Mr Netanyahu said: "I believe that's why you appreciate, Mr President, that Israel must reserve the right to defend itself." He went on to add that Israel must remain "the master of its fate".

And speaking later at the American-Israel Public Affairs Committee (Aipac), Mr Netanyahu reiterated that Israel was "determined to prevent Iran having nuclear weapons".

He stressed that all options were "on the table, but containment is not an option".

"The Jewish state will not allow those who seek our destruction the means to achieve that goal. A nuclear armed Iran must be stopped," Mr Netanyahu told Aipac.

Mr Obama and Mr Netanyahu are said to have a famously cool relationship. In May 2011, during a visit to Washington, correspondents widely noted the frosty body language between the two leaders.

Both men know that a lack of unity can only benefit a common enemy. But the disagreement between them is profound Obama and Netanyahu play down differences

In November 2011, at a G20 summit, journalists overheard a private exchange between French President Nicolas Sarkozy and Mr Obama in which Mr Sarkozy called the Israeli leader a "liar".

Mr Obama replied: "You may be sick of him, but me, I have to deal with him every day."

After years of international pressure and the repeated failure of negotiations and offers of talks with Tehran, talk has grown in recent months of a pre-emptive strike against Iranian nuclear facilities.

The US has pushed for the imposition of ever-stricter sanctions against Iran, including recent curbs on its central bank and its ability to export oil to the West.

If President Obama sticks to his current position... Prime Minister Netanyahu might decide to take a shot at Iran sooner

Yet despite the ratcheting up of sanctions, speculation has been mounting that Israel might choose to attack Iran sometime during 2012.

Hours before the two leaders held bilateral meetings the head of the UN nuclear agency, Yukiya Amano, reiterated that the organisation had "serious concerns" that Iran could be hiding secret work on developing atomic weapons.

Reiterating concerns detailed in an agency report, he said the organisation was unable "to conclude that all nuclear material in Iran is in peaceful activities".

'No hesitation'

In his speech on Sunday to Aipac, Mr Obama said the US "will not hesitate" to use force to stop Iran obtaining nuclear weapons.

But he stressed that diplomacy could still succeed.

"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," Mr Obama told the conference.

"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."

However, he said Iran was isolated and there was an opportunity "for diplomacy - backed by pressure - to succeed".

"Already, there is too much loose talk of war," Mr Obama added.

"Over the last few weeks such talk has only benefited the Iranian government, by driving up the price of oil which they depend upon to fund their nuclear programme."