One of six men alleged to be part of an al Qaeda sleeper cell in Lackawanna, N.Y., pleaded guilty to a reduced charge yesterday in exchange for an agreement to testify against his fellow defendants, marking what prosecutors described as an important breakthrough in the case.

Faysal Galab, 26, a U.S. citizen of Yemeni descent, pleaded guilty in the Western District of New York to a charge of providing "funds and services" to al Qaeda and its leader, Osama bin Laden, by attending a terrorism training camp in Afghanistan in the spring of 2001.

If Galab cooperates fully, including offering his testimony and submitting to military and law enforcement interviews, federal prosecutors will recommend a sentence of seven years in prison. Galab had faced twice as many years under the original charges.

U.S. Attorney Michael Battle called the deal "an important step in the successful prosecution of these defendants."

"Those who see fit to provide their money or services to support America's enemies, even if they are American citizens themselves, will face the full force of America's justice," Attorney General John D. Ashcroft said in a statement.

Galab admitted as part of the agreement that he had attended the al Farooq training camp in Afghanistan in April and May 2001, along with the five other Yemeni Americans in their twenties from the steel town of Lackawanna outside Buffalo.

Bin Laden visited the camp while the men were there, taking credit for the 1998 bombings of two U.S. embassies in East Africa and saying "that 50 men were on a mission to attack America," according to new details included in court documents yesterday. Four months later, 19 al Qaeda hijackers carried out the Sept. 11, 2001, attacks on the World Trade Center and Pentagon.

The alleged ringleader of the Lackawanna cell was another Yemeni American, Kamal Derwish, who was believed to have been killed in a CIA airstrike targeting a top al Qaeda leader in Yemen on Nov. 3. Derwish was an unindicted co-conspirator in the Lackawanna case.

The remaining defendants face up to 15 years in prison for allegedly providing material support to terrorists. They are Sahim Alwan, 30; Yahya Goba, 25; Yasein Taher, 25; Shafal Mosed, 24; and Mukhtar al-Bakri, 22.

Prosecutors and FBI officials say the men were awaiting orders from al Qaeda to carry out a terrorist attack in the United States, and that they received as much as six weeks of training in the use of explosives, assault rifles and handguns at al Farooq. Prosecutors also suggested that al-Bakri traveled to Bahrain last summer to possibly plot a large attack.