The man wanted by the United States as the mastermind of the Achille Lauro hijacking is a veteran of the often bloody politics of the Palestinian movement who aligned himself with Yasser Arafat in 1983 when the Palestine Liberation Organization split.

Mohammed Abbas Zaida, code-named Abu Abbas, told Egypt's Middle East News Agency in an interview in Belgrade today that the four men who hijacked the ship were on a "suicide mission" aimed at Israel when they were discovered and were "forced" to seize the ship.

"Their mission was not to hijack the Italian ship or to threaten the lives of the passengers," Abbas was quoted as saying. "Their destination was the Israeli port of Ashdod for the purpose of carrying out a suicide mission" inside Israel.

Abbas in the interview repeated denials that the four gunmen were responsible for the death of American passenger Leon Klinghoffer.

The faction of the Palestine Liberation Front that he heads issued similar denials in a statement.

In an interview with CBS radio, Abbas said by telephone from Belgrade that he would be willing to go to the United States "to clear my name" and explain everything if President Reagan guaranteed him safe conduct.

Abbas, who is believed here to have ordered, or at least persuaded, the four gunmen to return the Achille Lauro to Port Said Tuesday night, went on to play a central role in reaching the accommodation that led to the gunmen leaving the ship.

The four gunmen were identified at the outset as being of the Palestine Liberation Front, which also has said in a statement issued here that its operatives were involved. Abbas is head of the PLF wing that is close to Arafat and holds membership in his PLO. Syrian-based offshoots of the group have criticized the operation. Abbas publicly has defined his role in the affair as having been dispatched by Arafat to resolve the hijacking.

"When I went on board after completing negotiations with the four Palestinians," Abbas told the Egyptian news agency, "I asked the captain whether there were any injuries among the passengers and crew, and the captain said there were none."

The PLF statement issued in Beirut, went further, claiming that Klinghoffer, 69, had "suffered a heart attack and was taken to the ship's infirmary. After that we do not know how he disappeared or who made him disappear."

"We ask the whole world: what interest do our comrades have in killing an old and handicapped man?" the PLF statement said.

A U.S. diplomat in Cairo raised a point of caution on the PLF statement noting that the Arafat wing of the PLF might be expected to issue statements in Tunis, the site of the PLO headquarters, Washington Post correspondent Christopher Dickey reported.

While U.S. officials have yet to detail their evidence against Abbas publicly, those who know him well here say that using a ship as a way to get a guerrilla team through Israeli defenses would be very much in his style of operation.

The 38-year-old native of the Haifa area, for years identified with the most radical elements of the Palestinian movement, was named to the executive committee of Arafat's mainstream PLO a year ago and is said to serve on its 10-member inner cabinet.

Abbas' early identification was with Syria, where he spent his early years and went to a university. His first ties to Palestinian politics and guerrilla actions have been traced to 1965, when he joined forces with a group headed by Ahmed Jibril.

In alliance with the forces of George Habash's Popular Front for the Liberation of Palestine, Abbas and Jibril became identified with a series of hijackings and other incidents directed at attacking Israel proper. They became the militants of the Palestinian movement.

Their odyssey in militant Palestinian politics carried them to Jordan and then to Beirut, where friction between the two developed and festered until 1977, when they split. Abbas took most of their forces with him and became identified with the PLF. The tipping point seemed to be sentiments for or against Syria.

Jibril, now leader of the pro-Syrian Popular Front for the Liberation of Palestine-General Command, is believed to have been behind an assassination attempt against Abbas in 1978, when a bomb leveled a huge apartment building in the Fakhani section of Beirut. Abbas, who normally would have been in the building, had been delayed at a meeting.

Abbas' men are believed to have continued their attacks on Israel, with one particularly gruesome incident involving the only prisoner in Israel named by the four pirates among 50 they said they wanted freed.

In a 1979 raid at Nahariya in northern Israel by a four-man PLF squad, two Israelis, a man and his 5-year-old daughter, were killed. After the arrest of Samir Qantari, the only gunman to survive, the mother of the family emerged from hiding to find that her baby had suffocated when she tried to stifle its cries to keep from being discovered.

Other incidents attributed to the PLF include attempts to elude Israeli border security by using hang gliders and hot-air balloons.

Abbas had fled to Tunis along with Arafat when the PLO was chased from Lebanon by Israeli forces. While he is believed to hold to his more militant beliefs, Arafat kept him within the PLO umbrella, naming him to the PLO leadership.

U.S. officials insist that Abbas knew and directed the Achille Lauro gunmen, and Israeli officials insist that because of the ties between them, Arafat must have known of the PLF operation.