Iran's supreme leader ruled out Wednesday Iranian help in any United States-led attack on neighboring Afghanistan, calling U.S. behavior "disgusting" and saying that the U.S. was not "competent" to lead a global campaign.

"Iran will not participate in any move under U.S. leadership. Iran will not extend any assistance to the U.S. and its allies in attacking the already suffering Muslim neighboring Afghanistan," Ayatollah Ali Khamenei said in an address to families of soldiers killed in the 1980-88 Iran-Iraq war.

America's behavior, by expecting help but not earning the respect of other nations, was "disgusting," Khamenei said, adding that Iran did not consider the United States "competent and sincere (enough) to lead any global campaign against terrorism."

Khamenei's remarks were the clearest made yet by Iran in response to suggestions that Washington may call on Iran to join a U.S.-led global force to fight terrorism. Iran considers the United States its biggest enemy, but a strong reform movement in the government favors warming ties with the West. Washington has put Iran on a list of nations supporting terrorism.

During the past few days, Iran expressed its opposition to unilateral retaliatory U.S. military strikes against the Taliban, who harbor Usama bin Laden, the prime suspect in the Sept. 11 terrorist attacks. Iran has called for an international anti-terror coalition led by the United Nations — not Washington.

In his speech, Khamenei, the leader of hard-liners opposed to reforms, also rejected America's declaration to the world that nations had to choose between being "with us or terrorism."

"We are not with you," he said. "At the same time, we are not with terrorists. America is not sincere in fighting terrorism. It has other objectives. America's hands are stained with all the crimes committed by the Zionist regime," he said.

Iran, which steadfastly opposes Israel in its occupation of Palestinian territories and use of military force against Palestinian protesters, accuses Washington of being biased toward the Jewish state.

The United States wants Mideast support — from use of military installations or airspace to intelligence — as it builds forces for an expected assault on bin Laden's operations in Afghanistan.

The Associated Press contributed to this report.