U.S. Defense Secretary Donald Rumsfeld says some top Taleban and al-Qaida leaders may have fled to Iran. But the Secretary Rumsfeld says he has no hard information that any top Taleban or al-Qaida leaders are in Iran or that Iranian authorities have knowingly granted any of them sanctuary.

In an interview with The Baltimore Sun, released Friday, Mr. Rumsfeld said Iran is where some have "undoubtedly" fled. He noted that Iran has a long border with Afghanistan. He also said it has been used by the Taleban and al-Qaida as a transit route in the past.

Mr. Rumsfeld's statement marks the first time a senior U.S. official has named Iran as a possible destination for fugitive Taleban and al-Qaida leaders.

In the interview, the U.S. Defense Secretary said American forces have so far found no evidence of chemical, biological or nuclear weapons at any of nearly 50 suspected sites for such weapons in Afghanistan.

However he said that at one location, investigators found artillery shells made of depleted uranium, a heavy metal that is slightly radioactive.

He said several other sites turned out to be processing facilities for heroin.

Mr. Rumsfeld said U.S. and Afghan forces are meanwhile continuing to search caves and other hiding places in the Tora Bora region of Afghanistan for al-Qaida fighters. He says it will probably take until the end of January to complete the search.

For the moment, he says there are no plans to send in additional American soldiers to join the hunt. But he says that remains an option if necessary.

He also said U.S. and Afghan forces continue to search actively for Taleban leader Mullah Mohamed Omar, who he believes is still somewhere in Afghanistan.

Mr. Rumsfeld says U.S. forces would like to capture both Mullah Omar and al-Qaida leader Osama bin Laden.

But he again stressed that the capture of Osama bin Laden alone will not end the al-Qaida terrorist network, blamed for the bloody September 11 attacks on the United States.