Suleiman Franjieh, a stern Christian warlord who was President of Lebanon from 1970 to 1976, died early yesterday in the hospital of the American University in Beirut, which he entered three weeks ago. He was 82 years old and lived in the northern town of Zgharta, southeast of Tripoli.

He died of acute pneumonia and had heart and stomach ailments, an employee of the university said. The employee did not identify himself.

Mr. Franjieh, a Maronite Catholic, was a longtime ally of Syria, which is now the chief power broker in Lebanon. In this he differed from most Maronite leaders, who have had ties to Israel.

His clan holds sway in a mountainous area of northern Lebanon. For years its power has been enhanced by a group known as The Giants, which was formerly called an army or a militia. Since the militias in Lebanon were dissolved in 1990, the group has been calling itself a political party. Its current membership is estimated at 1,500 or more. Known for His Temper

Mr. Franjieh was known in Lebanon as "the tough man" because of his harsh tongue, volatile temper and ruthless treatment of some opponents. He was President in 1975, at the outset of the 15-year Lebanese civil war, in which he aligned himself with right-wing Christians against leftist Muslim groups and the Palestinians.

Some of his critics contended that Lebanon's decline into that civil conflict was hastened by corruption and the wielding of force against political foes during his presidency, and by vacillation on his part.

David Lamb, an American journalist, wrote in his 1987 book "The Arabs: Journey beyond the Mirage" that in the period leading up to the war, "President Suleiman Franjieh, a violent Christian of the right whose living-room walls were decorated with daggers, swords and rifles, was helpless in attempts to control" the Palestine Liberation Organization "or to stop Israeli infringement on Lebanese sovereignty, and his vacillation encouraged the Muslim groups to start kidnapping Christians and skirmishing with the Christian-led army."

"Christian hatred of the Palestinians grew," Mr. Lamb went on. "The lines for civil war were drawn."

The conflict then broke out and continued for a decade and a half, leaving thousands dead. Mr. Franjieh emerged from it isolated in his northern fief. There he maintained his rule for years despite the fact that he was at odds with his country's other powerful and warlike Maronite leaders.

Mr. Franjieh was born in Zgharta on June 15, 1910. After schooling at Antoura, near Beirut, he entered the export-import business in Beirut for a time. For years he was overshadowed by his elder brother Hamid, who headed the Franjieh clan.

In 1957, Suleiman Franjieh was accused in the machine-gun slaying of more than a score of members of a competing clan, the Douaihys, in a church not far from Zgharta. He then took refuge in the Syrian coastal city of Latakia, and there he became friends with two Syrian army officers, Hafez and Rifaat al-Assad. Hafez al-Assad went on to become the leader of Syria, with Rifaat as a key aide. Mr. Franjieh benefited greatly from the two Syrians' backing and protection in later years.

Before long, Mr. Franjieh was able to return to Lebanon and there he took over for his brother Hamid, who died in 1957. He was elected to Hamid's old seat in the Lebanese Parliament in 1960, held several Cabinet posts and gave up his seat in 1970, when he was elected President. Son Was Slain

In June 1978, Mr. Franjieh's life was changed when the principal Christian militia, the Phalange, raided Mr. Franjieh's summer home and killed his son Tony, Tony's wife, their young daughter, and a number of bodyguards.

Ever since then, Mr. Franjieh is said to have been depressed. He swore to take revenge on the slayers, declaring in an interview "the family will exact its retribution."

By some accounts, he went on to engineer the killing of hundreds of Phalange members. He also gradually transferred power to a grandson, Suleiman Franjieh, Jr. -- Tony's son, now 26 years old.

The elder Suleiman Franjieh's final appearance on the Lebanese national political stage came in 1988, when he made a brief bid to succeed President Amin Gemayel whose term ended that year. Two years later, the younger Suleiman Franjieh, affirming his own power within the Franjieh realm, declared that its militia had come under his control.

The elder Suleiman's survivors include his Egyptian-born wife, Iris; a son, Robert; and three daughters, Lamia, Sonia and Maya. The coffin containing Mr. Franjieh's body was taken to Zgharta for burial beside Tony Franjieh's grave.

Photo: Suleiman Franjieh (Associated Press, 1989)