Iran has closed the office of a former Afghan warlord who opposes Afghanistan's interim government and the strong U.S. role in that country, one of his aides said Sunday.

The closing of Gulbuddin Hekmatyar's offices in the Iranian capital, Tehran, and the eastern city of Mashhad appears to be a conciliatory gesture toward the United States, where officials have accused Iran of trying to destabilize the new Afghan government.

The aide, who spoke to The Associated Press on condition of anonymity, would not give details about the closure, and Iranian officials did not immediately respond to a request for comment.

Hekmatyar, a former Afghan prime minister living in exile in Iran, has rejected the U.N.-brokered accord that established the new Afghan administration led by Hamid Karzai, saying the pact negotiated in Germany amounted to a U.S.-imposed government.

On Wednesday, Secretary of State Colin Powell accused Iran of trying to destabilize the fragile post-Taliban government. U.S. officials have repeatedly said Tehran gives refuge to anti-government figures or supports them in Afghanistan. Iran has denied the accusations.

Iran's Interior Minister Abdolvahed Mousavi Lari said the same day that Iran was considering whether to kick out Hekmatyar.

Iran has insisted that it supports Karzai's government, which is to run the country until June. Still, some observers say Iran, like others among Afghanistan's neighbors, is jockeying for influence among the various factions within the country.

Iran is believed to be concerned by Washington's growing influence in Afghanistan, where a U.S. bombing campaign last year helped bring Karzai to power.

Iran also has become concerned that it may be a new target in the U.S. war against terror after President Bush accused it of belonging to an "axis of evil" that supports terrorism and seeks to develop weapons of mass destruction, charges that Tehran denies.

Early in the U.S. war on terrorism, American officials spoke of better cooperation with Iran. But in the past month, Bush has accused Iran of interfering to undermine Afghanistan's new government. Washington has also been angered by an alleged attempt to smuggle Iranian weapons to the Palestinians.

In recent days, newspapers and Iranian state-run radio and television have been calling for a nationwide anti-American rally Monday to mark the 23rd anniversary of the Islamic revolution, which swept U.S.-backed Shah Mohammed Reza Pahlavi from power.

"One of the goals of recent American threats is to frighten the Iranian nation and authorities, so tomorrow's rally is extremely important and decisive and I have no doubt that the people will give a strong response to the enemy by attending the rally," Iran's supreme leader Ayatollah Ali Khamenei said Sunday, according to state-run Tehran radio.

Even reformist President Mohammad Khatami, who has in the past called for unofficial dialogue with the Americans, said the rally was a sign of Iran's resolve.

"Considering the baseless, incorrect and insulting statement against the Iranian nation and revolution this year, I'm sure the people tomorrow will show their loyalty to the revolution," Khatami told Iranian television Sunday.