About 100 Lebanese living in the United States gathered quietly yesterday under the shadow of the Iwo Jima Memorial to hold a mass in memory of the four U.S. Marines who died in the conflict in Lebanon.

Standing amid fluttering Lebanese and American flags, they took communion, while Salim Fahed, a former seminary student, sang a communion song in Arabic.

After the breaking of the bread by the Rev. Mark Heath, a Dominican priest, Roy Salameh, a graduate student in finance at George Washington University, walked up to the makeshift pulpit.

"We would like to send our deepest condolences to the families and to the American people in general. We share their sorrows and sadness," said Salameh. "God bless all of you. God bless America. God save Lebanon."

The mass was the culmination of a three-day effort organized by the Lebanese Students Association of America to counteract growing pressure by some American groups to pull the Marines out of Lebanon.

"It is our way of thanking the Marines who are giving their lives to save the people of Lebanon," said William Nicholas, a Lebanese electrical engineering graduate student at George Washington University.

Fahed said the Marine Corps Memorial in Arlington was chosen as the site of the mass because it was the "symbol of the Marines who had died overseas to protect liberty."

The mass by Father Heath stressed peace and forgiveness. But the private conversations focused more on the desires for victory and retaliation against Syria and against the Druze and Shiite Moslem militia who are challenging the Christian-dominated government of Amin Gemayel.

"We are trying to do whatever we can to draw people's attention to what is happening in Lebanon," said Tony Khoury, a civil engineering student at George Washington, who said he has not been able to reach his family for two weeks. "It is time that the people here opened up their eyes to what is happening in Lebanon."