Calling Iran a danger to the U.S. and one of Israel's greatest threats, Sen. Hillary Rodham Clinton said Thursday that "no option can be taken off the table" when dealing with that nation.

"U.S. policy must be clear and unequivocal: We cannot, we should not, we must not permit Iran to build or acquire nuclear weapons," Clinton told a crowd of Israel supporters. "In dealing with this threat ... no option can be taken off the table."

Clinton, D-N.Y., spoke at a Manhattan dinner held by the nation's largest pro-Israel lobbying group, the American Israel Public Affairs Committee. Some 1,700 supporters applauded as she 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," Clinton said, criticizing what she called the Iranian administration's "pro-terrorist, anti-American, anti-Israeli rhetoric."

Iranian President Mahmoud 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. 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.

Clinton, the front-runner for her party's presidential nomination, called for dialogue with foes of the United States, saying Iran "uses its influence and its revenues in the region to support terrorist elements."

"We need to use every tool at our disposal, including diplomatic and economic in addition to the threat and use of military force," she said.