U.S. authorities have arrested the alleged mastermind of the 1993 bombing of the World Trade Center and are holding him in New York for trial, the Justice Department announced last night.

Ramzi Ahmed Yousef, 27, was detained Tuesday by law enforcement officials in Pakistan and was handed over yesterday to American authorities there. Yousef was flown to the United States last night and is scheduled to be arraigned in federal court in Manhattan today, officials said. He was indicted March 11, 1993, for the Feb. 26, 1993, bombing in which six people died and more than 1,000 were injured.

President Clinton last night hailed the arrest as "a major step forward in the fight against terrorism. Terrorism will not pay. Terrorists will pay. We will continue to work with other nations to thwart those who would kill innocent citizens to further their own political aims."

Authorities said a lead in their worldwide pursuit of Yousef came last month in the Philippines with the arrest of two of his alleged accomplices in making bombs for airplanes and for plotting the assassination of Pope John Paul II when he visited Manila. Yousef, however, escaped the Philippines under an alias.

Four of Yousef's codefendants -- Mohammad Salamed, Nidal Ayyad, Mahmud Abouhalima and Ahmad Mohammad Ajaj -- were convicted of federal charges last March and each was sentenced to 240 years in prison.

The indictment charges Yousef with 11 counts in the World Trade Center bombing; if convicted, he could be imprisoned for life without possibility of parole. According to the indictment, Yousef flew to New York from Pakistan in September 1992 and later purchased chemicals that were delivered to a storage shed in Jersey City, N.J. Authorities said that is where the chemicals were kept before being loaded into a rented van that exploded in a parking garage beneath the trade center.

After Yousef, using an alias, fled on the day of the bombing, the United States posted a $2 million reward for his return. It was unclear last night who might collect the reward. Authorities said the U.S. Drug Enforcement Administration, the FBI and the State Department's Diplomatic Security Service learned that Yousef would be coming to Pakistan and alerted Pakistani officials, who detained him when he arrived there, U.S. officials said. The Pakistanis then turned him over to the FBI.

During their investigation of the trade center bombing, authorities said they believed Yousef came to New York solely to enlist participants in a terrorist conspiracy and to commit a terrorist act. Yousef, an Iraqi national, frequented the Jersey City and Brooklyn mosques where the militant Sheik Omar Abdel Rahman preached, and authorities said they believe he did that to meet like-minded Muslims.

Yousef arrived in New York in September 1992 on the same Pakistan International Airlines flight as Ajaj. Yousef used an Iraqi passport giving his name as Azan Muhammad. His credentials appeared in order, according to airline officials, and neither his real name nor the alias -- allegedly one of 10 he had used -- appeared on any U.S. watch list for terrorists.

Ajaj, however, was arrested when they landed in New York for carrying a fake Swedish passport, and authorities confiscated manuals he was carrying with instructions on how to build and use explosives. After serving six months in jail for the passport violation, he was released in March 1993. He was rearrested within a few days and charged with participation in the World Trade Center conspiracy.