Iran's supreme leader Ayatollah Ali Khamenei rejected any resumption of ties with the United States as a "humiliating" step that would jeopardize achievements made by the Islamic revolution.

Speaking to Iranian diplomats late Sunday, Khamenei said resuming ties with Washington would mean "losing a bright future and having the vital achievements of the revolution shattered," the official Islamic Republic New Agency reported.

"White House warmongers will either try to destroy the [Islamic] establishment, or to make conditions unbearable for Iran to force her to resume ties with America," the report quoted Khamenei as saying, without elaborating.

Khamenei's comments followed new calls by Iranian reformists, including a senior adviser to President Mohammad Khatami, for rapprochement with Washington. They also came as speculation mounts of a U.S. strike against Iran's neighbor, Iraq, on grounds that it is stockpiling weapons of mass destruction. Iran, like other Mideast states, is opposed to any such attack.

Khamenei, who has the final say on all Iranian state matters, often criticizes the United States and accuses it of forcing its will on other nations. He has repeatedly rejected talks with America.

Last week, Khamenei accused President Bush of addressing the world with the rhetoric of Nazi leader Adolf Hitler. On Sunday, he said the U.S. government's policies were of the "cowboy culture."

Iran and the United States severed diplomatic ties after militants stormed the U.S. Embassy in Tehran following the 1979 Islamic revolution.