Terror mastermind Osama bin Laden is in eastern Iran and not the rugged tribal areas of Pakistan's northwestern frontier where many believe him to be on the run, United States intelligence officials were on Monday quoted as saying.

In interviews to the Washington Times, the US officials said the Iran theory, which is held by a minority, is based on bits of intelligence information and the fact that months of Central Intelligence Agency operations, along with search-and-destroy sweeps by thousands of Pakistani troops have failed to find the Al Qaeda [Images] chief or his number two Ayman al-Zawahiri.

Asked whether the US intelligence community thinks Osama may be in Iran, a senior administration official told the paper, "Some people think he is."

That source said there is great frustration, especially within the inner circle around Defence Secretary Donald Rumsfeld, that Osama has not been caught or even unequivocally spotted in Pakistan's border region, which in turn fuels speculation that he may not be there at all.

Republican Congressman Curt Weldon, House Armed Services Committee member, writes in his new book, Countdown to Terror that a reliable Iranian source he identifies only as 'Ali' told him that Osama has been in Iran for some time.

"The course of world events," Weldon writes, "have established incontrovertibly that Ali is a high credible source of reliable intelligence on Iran and other terrorist activities."

The Bush administration's official position is that Osama is most likely in the border region straddling Pakistan and Afghanistan and that he is hidden by tribal allies.

"The consensus is that Osama remains in the border region," said a US intelligence official.