A U.S. citizen accused of being a Palestinian terrorist was extradited to Israel Tuesday night in the wake of precautionary State Department warnings that the move could trigger terrorist retaliation, possibly on a passenger ship in the eastern Mediterranean.

The suspect, Mahmoud Atta, 37, was transferred to Israeli custody in New York Tuesday evening "and departed the United States immediately thereafter on a flight to Israel," the State Department said.

Jailed in New York's Metropolitan Correction Center since his arrest three years ago, Atta faces trial in Jerusalem on charges of taking part in an April 1986 machine gun attack on an Israeli bus traveling through the occupied West Bank.

The State Department said he is a member of the Abu Nidal Organization (ANO) which U.S. officials have called "the most dangerous terrorist organization in existence." The ANO, the department said last Friday in issuing its threat advisory, "has repeatedly threatened to attack U.S. interests" if Atta is extradited.

The warning said that the risk of acts of international terrorism in Europe and the Middle East is increasing and that the government has received "specific and credible information regarding a possible terrorist threat to passenger ships operating in the eastern Mediterranean."

"Such an operation may be undertaken at any time," State Department deputy spokesman Richard Boucher said. He said U.S. officials were also "particularly concerned about aircraft operating in Europe or the Middle East."

Said another official familiar with U.S. intelligence reports, "It's their {the terrorists'} nickel. They pick the one they want to do. Plane or ship? They ask themselves, 'What's going to make the biggest splash?' "

Atta, also known in Israel as Mahmoud Abed Atta, was arrested by FBI agents at John F. Kennedy International Airport in 1987 on a flight from Venezuela. His lawyer, former U.S. attorney general Ramsey Clark, maintained that Atta was innocent and that the FBI had seized him illegally.

Atta was arrested entering Caracas on April 27, 1987, but because Venezuela has no extradition treaty with Israel, he was handed over to FBI agents who put him on a flight to New York and arrested him once he was within U.S. jurisdiction.

Two of Atta's cousins, now serving life terms for the bus attack, implicated him in sworn statements and described their mutual membership in the ANO. Clark contended that they implicated Atta only after an Israeli Shin Bet security squad had tortured them.

The driver of the bus, which was carrying Jewish settlers, was killed and a passenger injured in the attack. A federal judge in New York approved Att's extradition in September 1989 and the U.S. Supreme Court rejected his last appeal Aug. 31.

The State Department said it takes the ANO threats "very seriously in view of the ANO's notorious history." Officials say the group was responsible for more than 90 terrorist attacks since 1974, including the bombing of the airports in Vienna and Rome in December 1985.