A guilty plea yesterday by a man who attended a terrorist training camp in Pakistan will dramatically limit the scope of a multi-defendant terrorism trial scheduled for later this month in Manhattan.

Mahmud Brent, 32, traveled to Pakistan just months after the September 11, 2001, terrorist attacks to engage in military training with a terrorist organization. Following the training, Brent returned to America and moved to Maryland, where he studied to become a paramedic.

Brent’s pleaded guilty yesterday to conspiring to provide material support to a terrorist organization, a crime for which he faces up to 15 years in prison. The guilty plea marks his exit from a high-profile terrorism prosecution that at one point included three defendants in addition to Brent. Last November another defendant, an Islamic bookseller in Brooklyn, pleaded guilty. Neither of the men who pleaded guilty are expected to be called by the prosecution to testify, lawyers involved in the case say.

The two remaining defendants — a Harlem jazz player and a Columbia University educated doctor — are accused of swearing an oath of fealty to Osama bin Laden while in a Bronx apartment. The prosecution against them is the result of a sting operation that included an undercover FBI agent who posed as a recruiter for the terrorist leader.

Originally, the charges had been the result of two separate investigations, each involving separate confidential informants.

One of the informants, whom a defense lawyer identified last year as Mohamed Alanssi, set himself afire in front of the White House in 2004 in protest of his treatment by the FBI. Court files suggest that the informant at the center of the sting operation involving the musician and the doctor is not Mr. Alanssi, raising the question of whether prosecutors will need to call Mr. Alanssi as a witness.

Brent has not cooperated with the government, his lawyer, Hassen Ibn Abdellah, said following yesterday’s hearing. The possibility that Brent will play no role in the coming trial could be a plus for the two remaining defendants, Tarik Shah and Rafiq Sabir. Lawyers for the two had originally asked for separate trials partly on the grounds that Brent’s past history with a terrorist organization would prejudice the jury against Messrs. Shah and Sabir, who are not accused of having ties to terrorists overseas.

In court yesterday, Brent appeared in good spirits. He frequently turned around in his chair to smile broadly at the rows of family members and supporters who attended the hearing.

The group Brent was affiliated with, Lakshar-e-Taiba, was designated by America as a terrorist organization in December 2001, shortly before Brent’s arrival. Nevertheless, Brent testified yesterday that he knew of the group’s designation at the time of his trip.

Brent is a native of Ohio who lived in upstate New York before traveling to Pakistan.