Usama bin Laden allegedly sent out a handwritten letter to rally the Al Qaeda and assure them that the United States will be defeated, even as Afghanistan's foreign minister said he thinks the terrorist mastermind and his supporters are hiding in northwest Pakistan.

"We will closely witness, Allah willing, the fall of the United States of America, which ignored all human values, passed over all limits, and understands no logic but that one of power and Jihad,” bin Laden allegedly wrote in a letter obtained Saturday by IslamOnline.

The letter was allegedly written weeks ago and handed to the Web site by an Afghan source who requested not to be named. The source pointed out similarities between the blue-inked scrawl on the letter and samples of bin Laden's penmanship in the hands of the FBI and CIA.

Gen. Tommy Franks, head of the U.S. military's Central Command in Afghanistan, has said there is no "convincing proof" that bin Laden is dead, but said Sunday that if  bin Laden is alive "it's only a matter of time" before he is found.

On Sunday,  Afghan Foreign Minister Abdullah said bin Laden and the remnants of Al Qaeda and the Taliban still pose a threat from their hideouts across the border in Pakistan.

"They are mainly on the other side of our border, that is, in the northwestern frontier of Pakistan," Abdullah said of Al Qaeda and Taliban holdouts. "My perception is that Mullah Omar and bin Laden are somewhere in Pakistan."

The foreign minister, who like many Afghans uses only one name, said hunting down terrorists in Pakistan was up to that country's government.

"We should all focus more on Al Qaeda and former Taliban leaders. They are present in the region and they can pose threats in the future," Abdullah said. "The issue of the presence of Taliban leaders and Al Qaeda leaders in Pakistan is an issue for Pakistan to deal with."

He gave no proof to back up his claim, however.

There was no comment from Pakistani authorities to Abdullah's claim, but Pakistani officials have said in the past that they do not believe bin Laden or Mullah Omar are on Pakistani soil.

A U.S.-led coalition has been struggling to hunt down the two leaders and their supporters for months in the rugged hills and mountains that straddle the two nations' common border.

The Taliban were strongly backed by Pakistan's government for years. But Pakistan withdrew its support following the Sept. 11 terrorist attacks in the United States and joined the American-led war on terrorism.

Relations between Pakistan and Afghanistan -- controlled now in large part by northern alliance leaders who once opposed Pakistan -- have been awkward since the transitional government of President Hamid Karzai took power.

Abdullah said, however, that relations between the two neighbors had "entered a new phase" and "improved a great deal" in recent months.

In April, Pakistan President Gen.. Pervez Musharraf visited Kabul and met with Karzai. Abdullah was scheduled to visit Pakistan on Monday.

In March, a joint U.S.-Pakistan team captured Abu Zubaydah, believed to be the third-ranking figure in Al Qaeda, during a raid on a hide-out in the Pakistani city of Faisalabad.

In other news, the foreign minister said he would travel to New York with Karzai in September to commemorate the terrorist attacks which brought down the World Trade Center towers and the Pentagon.

Asked if he was concerned about recent statements by American commanders that U.S. troops could be in Afghanistan for years, Abdullah said simply: "I do not believe that the campaign against terror is a short term one."

The Associated Press contributed to this report.