JERUSALEM: President Barack Obama said Sunday that the United States will not hesitate to attack Iran with military force to prevent it from acquiring a nuclear weapon, but he cautioned that ''too much loose talk of war'' recently has only helped Tehran and driven up the price of oil.

Speaking to a powerful pro-Israel lobbying group, Obama appealed to Israel for more time to let sanctions further isolate Iran. He sought to halt a drumbeat to war with Iran and hold off a unilateral Israeli strike against Iran's nuclear facilities.

''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,'' Obama told thousands at the annual American-Israel Public Affairs Committee's policy conference. ''Now is the time to let our increased pressure sink in, and to sustain the broad international coalition that we have built.''

Quoting President Theodore Roosevelt, Obama said he would ''speak softly, but carry a big stick'' and warned Iran not to test US resolve.

Obama's widely anticipated speech came one day before he meets at the White House with Israeli Prime Minister Benjamin Netanyahu, who planned to address AIPAC late Monday.

Three Republican presidential candidates, Mitt Romney, Rick Santorum and Newt Gingrich, were scheduled to speak to the conference via satellite on Tuesday, a critical day in the primary campaign when 10 states vote in the race to find a challenger to Obama in the November election.

To Israel and to Jewish voters in this country, Obama promoted his administration's commitment to the Mideast ally.

''You don't have to count on my words. You can look at my deeds,'' Obama said. He defended his record of rallying to Israel's security and political sovereignty, saying: ''We have been there for Israel. Every single time.''

Obama's comments were heavily laced with the politics of the campaign. He blamed distortions of his record on partisan politics.

The Israeli president, Shimon Peres, spoke before Obama and said that a nuclear Iran would be a menace to the world, not just to Israel's security.

Peres, whose country sees its existence threatened by the potential development of nuclear arms by Iran, said: ''Iran is an evil, cruel, morally corrupt regime. It is based on destruction and is an affront to human dignity.'' He said Israel knows the horrors of war and does not seek one with Iran, ''but if we are forced to fight, trust me. We shall prevail.''

Iran claims its nuclear program is for peaceful purposes.

In Israel, Foreign Minister Avigdor Lieberman said American pressure would not affect Israeli thinking on how to cope with the threat.

''We are an independent sovereign state, and at the end of the day, the state of Israel will make the most correct decisions as we understand them.''