President Barack Obama has vowed that all options will remain on the table when it comes to US action against a nuclear Iran.

The US leader, speaking at the annual American Israel Public Affairs Committee (Aipac) conference in Washington DC, said he would be willing to consider "all elements of American power" to counter the Iranian threat.

"When it comes to preventing Iran from obtaining a nuclear weapon, I will take no options off the table, and I mean what I say," he told the conference.

Although he cautioned against counterproductive "loose talk of war", he added that options included " a political effort aimed at isolating Iran; a diplomatic effort to sustain our coalition and ensure that the Iranian programme is monitored; an economic effort to impose crippling sanctions; and, yes, a military effort to be prepared for any contingency.

"For the sake of Israel's security, America's security and the peace and security of the world, now is not the time for bluster."

He also reiterated his support for the Jewish state, telling the audience: "Whenever an effort is made to delegitimise the state of Israel, my administration has opposed them. So there should not be a shred of doubt by now: when the chips are down, I have Israel's back."

His speech was heavily praised by senior Israeli politicians, including Deputy Prime Minister Silvan Shalom , who said it was "almost perfect."

Prime Minister Benjamin Netanyahu expressed his gratitude for the president's pledges. "I appreciate the fact that he repeated his position that Iran should not be allowed to develop nuclear weapons and that all options are on the table," said the Israeli leader. "I also appreciate the fact that he said that on the Iranian issue, containment is not an option. But most of all, I appreciate that he said that Israel must be able to defend itself against any threat."

President Obama will meet Mr Netanyahu at the White House later today.