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."