9-11

The likely mastermind of the Sept. 11 attacks is a Kuwaiti-born lieutenant of Osama bin Laden who had previously plotted to attack the World Trade Center and to bomb several airliners simultaneously, a top U.S. counterterrorism official says.

Khalid Shaikh Mohammed, one of the FBI's most-wanted terrorists, is at large in Afghanistan or nearby, the law enforcement official told The Associated Press on Tuesday.

U.S. investigators believe Mohammed, working under bin Laden's leadership, planned many aspects of the Sept. 11 attacks.

''There's lots of links that tie him to 9-11,'' the official said, speaking on condition of anonymity. ''He was intricately involved.''

Mohammed is accused of working with Ramzi Yousef in the first bombing of the World Trade Center, which left six dead in 1993. He and Yousef also were accused of plotting in 1995 to bomb several trans-Pacific airliners heading for the United States. Yousef, now serving a life sentence in the United States after being convicted in the 1993 World Trade Center bombing, also is believed to have planned to crash a plane into CIA headquarters.

Mohammed was charged by federal prosecutors in New York in 1996 in connection with the alleged 1995 plot. The State Department is offering a reward of up to $25 million for information leading to his capture.

Other bin Laden lieutenants are also believed to have helped put together the Sept. 11 attacks, the official said. But evidence is mounting that Mohammed was at the center of the operational planning.

A second U.S. official, also speaking on condition of anonymity, acknowledged that Mohammed played a critical role in planning the attacks but said questions remain about the extent of his leadership. The official said other bin Laden lieutenants, including Abu Zubaydah, now in U.S. custody, are also believed to have played top organizational roles.

Mohammed, 36, is one of the highest-ranking al-Qaida leaders still at large, officials said,