Israeli Prime Minister Benjamin Netanyahu met US Secretary of State Hillary Clinton on Tuesday to discuss Iran's nuclear ambitions, and said he was leaving after "a very good visit" to Washington.

With the world focused on the possibility of a military strike on Tehran's atomic sites, Netanyahu met Clinton for talks that lasted an hour, a day after he made a hawkish speech to the pro-Israel lobbying group AIPAC.

"Unfortunately, Iran's nuclear program has continued to march forward. Israel has waited... for diplomacy to work, we've waited for sanctions to work. None of us can afford to wait much longer," Netanyahu said late Monday.

"As prime minister of Israel, I will never let my people live in the shadow of annihilation," he told 13,000 delegates at the conference.

The talks with Clinton followed Monday's discussion with President Barack Obama, who said diplomatic efforts with Iran should continue.

While Clinton has voiced exasperation in the past over settlement building in the occupied West Bank and east Jerusalem under Netanyahu, the Israeli leader enjoys strong bipartisan backing on Capitol Hill.

Netanyahu praised Congress during his AIPAC speech, saying that more than half the members of the legislature were guests in the audience.

After meeting Clinton, Netanyahu held talks with congressional leaders.

"We've had a very good visit in Washington, first in our discussion with the president in the Oval Office... and now culminating in this remarkable display of solidarity here in the Congress of the United States," he said.

"I go back to Israel feeling that we have great friends in Washington."

House Speaker John Boehner, a Republican, said: "The looming threat of a nuclear Iran cannot be ignored. Now is the time to stand together and we are here today to tell the prime minister that Congress intends to do so."

Obama, however, dismissed criticism that his policy on Iran had been too casual, saying the "bluster" coming from rival Republicans in this presidential election year was not helping solve the nuclear standoff.

"This is not a game, and there is nothing casual about it," Obama told reporters.

US Defense Secretary Leon Panetta, meanwhile, pledged to continue strong American backing for Israel's military, saying the aid had increased "dramatically" under Obama's administration.

"This is an ironclad pledge which says that the United States will provide whatever support is necessary so that Israel can maintain military superiority over any state or coalition of states, as well as non-state actors," Panetta said in a speech at AIPAC.

In Brussels, EU foreign policy chief Catherine Ashton, speaking on behalf of China, France, Germany, the Russian Federation, the United Kingdom and the United States, reiterated an offer to resume talks with Tehran.

The Obama administration says it does not believe Iran has taken a decision to develop a nuclear weapon, or that the time is right for military action, preferring to give biting new sanctions time to work.

But Israel, which sees a possible Iranian nuclear weapon as a threat to its very existence, claims Iran may be on the cusp of "breakout" capability -- when it could quickly build a nuclear weapon.

In his speech to AIPAC, the American Israel Public Affairs Committee, Netanyahu sought to minimize the differences between himself and Obama.

Obama "stated clearly that all options are on the table and that American policy is not containment," Netanyahu said. "Israel has exactly the same policy."

Netanyahu said that for the world to allow Iran -- which he said was dedicated to the destruction of the Jewish state -- to attain a nuclear arsenal evoked memories of US refusal in World War II to bomb the Auschwitz Nazi death camp to prevent the mass extermination of Jews there.

Netanyahu also told Obama on Monday that Israel must remain the "master of its fate," in a firm defense of its right to mount a unilateral strike on Iran.

Obama, who assured Netanyahu that he has Israel's "back," stressed that he sees a "window" for diplomacy with Iran, despite rampant speculation that Israel could soon mount a risky go-it-alone military operation.