The explosion that killed a U.S. Marine serving with the multinational peace-keeping force in Beirut Thursday came from an American-made cluster bomb shell supplied to the Israeli Army, a U.S. Army spokesman confirmed here today.

Lt. Col. Lee DeLorme Jr. said an investigation into the accident, which also wounded three other Marines, had concluded that the object was one of the "bomblets" contained in a 155-mm shell called an "improved conventional munition."

The widespread Israeli use of the cluster bombs against Palestinians during the war this summer caused a major controversy in the United States, which led to the Reagan administration's suspending the shipment of any more such weapons to Israel.

DeLorme said the three wounded Marines were in "good to excellent" condition.

Reuter reported from Washington that Lebanese President Amin Gemayel, brother of the slain president-elect, will meet with President Reagan at the White House Oct. 19. The Lebanese president is also scheduled to meet with Pope John Paul II and French President Francois Mitterrand during the same foreign tour.

The Associated Press reported from Damascus that U.S. special envoy Philip C. Habib conferred with Acting Foreign Minister Farouk Chare for two hours Saturday. Habib arrived in Syria Friday from Beirut, following a swing through the Middle East that involved visits to Israel, Jordan, Saudi Arabia and Egypt.

Meanwhile, the new local Central News Agency disclosed more details today about the arrest of the alleged assassin of president-elect Bashir Gemayel Sept. 14 and identified him as Habib Shartouni.

The agency said he was a member of the Lebanese leftist Syrian Socialist National Party, which has close ties to the Syrian government and that he was an operative of both the Palestinian and Syrian intelligence services inside Lebanon.

This seemed a further indication of possible Syrian involvement in the assassination, although Gemayel's Phalangist Party has not yet named the "foreign quarters" that it said yesterday were implicated.

The Central News Agency has close ties with the Phalangist Party and has been providing most of the information so far about the Phalangist investigation into Gemayel's murder.

The agency also said Shartouni's grandfather was the landlord of the apartment building where Gemayel was killed by a bomb blast. This would explain how Shartouni might have been able to enter the building and place the 77-pound charge in a room directly above the place where Gemayel had been speaking.

It was learned today that Shartouni was arrested by the Phalangists a day after the assassination as he allegedly was trying to flee toward the Syrian-controlled area of eastern Lebanon.