BALTIMORE (AP) – Republican presidential candidate Mitt Romney on Friday accused Democratic front-runner Senator Clinton, Democrat of New York, of “timidity” regarding the security threat posed by Iran.

In a speech to a retreat of conservative congressional Republicans, Mr. Romney lashed out at Mrs. Clinton for telling a pro-Israel dinner that a dialogue with countries hostile to Israel – including Iran and Syria – is needed to promote peace in the Middle East.

“At this point, We don’t need a listening tour about Iran,” Mr. Romney told the Republican Study Committee. “Someone who wants to engage Iran displays a troubling timidity toward a terrible threat of a nuclear Iran.”

In a speech Thursday night at a Manhattan dinner held by the nation’s largest pro-Israel lobbying group, the American Israel Public Affairs Committee, Mrs. Clinton called Iran a danger to the U.S. and one of Israel’s greatest threats.

But the New York senator also said, “We need to use every tool at our disposal, including diplomatic and economic in addition to the threat and use of military force” when dealing with Iran.

“I have advocated engagement with our enemies and Israel’s enemies,” Mrs. Clinton said. “I believe we can gain valuable knowledge and leverage from being part of a process again that enables us to get a better idea of how to take on and defeat our adversaries.

“U.S. policy must be clear and unequivocal: We cannot, we should not, we must not permit Iran to build or acquire nuclear weapons,” Mrs. Clinton told the audience. “In dealing with this threat … no option can be taken off the table.”

Responding to Mr. Romney’s criticism, Mrs. Clinton spokesman’s Mo Elleithee said Friday: “Senator Clinton believes that no option should be taken off the table when it comes to preventing Iran from developing nuclear weapons. Given his record of flip flops, the only thing that’s timid are Governor Romney’s convictions.”

Mr. Romney, who served one term as Massachusetts governor, said that rather than engagement, economic and diplomatic isolation should be the priority.

Last year, when former Iranian President Khatami visited Harvard University, Mr. Romney criticized the visit and ordered state agencies not to cooperate if asked for assistance.

On Thursday, some 1,700 attendees applauded as Mrs. Clinton cited her efforts on behalf of the Jewish state and spoke scathingly of Iran’s decision to hold a conference last month that questioned whether the Holocaust took place.

“To deny the Holocaust places Iran’s leadership in company with the most despicable bigots and historical revisionists,” Mrs. Clinton said, criticizing what she called the Iranian administration’s “pro-terrorist, anti-American, anti-Israeli rhetoric.”

Iranian President Ahmadinejad has repeatedly called the Holocaust a “myth” and said Israel should be “wiped off the map” and its Jews returned to Europe.

Iran insists its nuclear program is designed to produce energy, not weapons. Mr. Ahmadinejad said Thursday that his government is determined to continue with its nuclear program, despite U.N. Security Council sanctions imposed over its refusal to halt uranium enrichment, a process that can produce fuel to generate electricity or for the fissile core of an atomic bomb.

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Associated Press Writers Samantha Gross and Beth Fouhy in New York contributed to this report.