French Ambassador Louis Delamare, one of the most respected foreign diplomats in Lebanon, was assassinated today in a daring midday ambush near his home in West Beirut, hard by the no man's land that separates the Christian east from the Moslem west in this violent capital.

The popular 59-year-old ambassador, who had shunned the armored, bulletproof cars most of his colleagues favor, was killed after gunmen in another car forced his chauffeured limousine to the curb in an apparent kidnap attempt. The car was 200 yards from the entrance of his home, where he was headed for lunch.

A trio of gunmen tried to get the ambassador out of his gray Peugeot 604 sedan. When he refused to unlock the doors, they trained their pistols and one automatic rifle through the right rear window and opened fire.

The ambassador crumpled in his seat from six bullet wounds in the head and abdomen, while his assailants jumped back in their own white BMW sedan and sped southward, losing any pursuers in traffic.

The ambassador's chauffeur, shaken but unscathed, rushed Delamare to the nearby Barbir Hospital, where he died an hour later on the operating table.

Officially, neither the Lebanese authorities nor French diplomats would discuss suspicions they might have of who may have been behind Delamare's killing. No group stepped forward to claim responsibility.

But some still-stunned French diplomats speculated in private that the only obvious candidates were local supporters of Ayatollah Ruhollah Khomeini's Islamic revolution of Iran.

Iran, these diplomats note, has both denounced and threatened France for its decision recently to grant political assylum to former Iranian president Abol Hassan Bani-Sadr and Massoud Rajavi, the head of the Iranian urban guerrilla group Mujaheddin-e-Khalq (People's Warriors), which has been waging a war of assassination against Khomeini's regime.

In the chaotic political cauldron that is Beirut there is no regional government, party or faction that does not have its own proxy forces, armed and organized, to do its bidding. Iran is no exception and is known to have followers not only among the local Shiite militia, Amal, here but also in various other shadowy groups.

Since last December, the French Embassy on West Beirut's Rue Clemenceau has been shelled twice in the night with rockets. Each time, a heretofore unknown group calling itself the Mujaheddin-Saff (The Warrior's Rank) had claimed responsibility for the attacks.

The first attack Dec. 27, the group said in messages to a local newspaper, was to protest France's granting of asylum to former Iranian prime minister Shahpour Bakhtiar. The second attack, the group told the same newspaper in April, was to protest France's sale of Mirage jets to Iraq, with whom the Iranians are warring.

Delamare, a former spokesman for the French Foreign Ministry, only five days ago played host to French Foreign Minister Claude Cheysson here.

The shooting today came only hours after a special Arab League ministerial "follow-up" committee ended a two-day meeting, its fifth on untangling Lebanon's violent politics since a shaky cease-fire was established in June.

The committee, chaired by President Elias Sarkis, and composed of Arab League Secretary General Chedli Klibi and the foreign ministers of Saudi Arabia, Kuwait and Syria, reported agreement on setting up machinery to establish "effective control over the country's porous Mediterranean ports to prevent any further shipments of weapons to Lebanon, except those destined for the government's own Army and security forces."

The underlying principle is that if such control is established, Israeli arms shipments to the Christian Lebanese militia of Bashir Gemayel in East Beirut would be halted, as would other arms shipments to various Moslem militias and Palestinian guerrillas.

It was widely noted, however, that nothing was said in the agreement about overland arms deliveries. Diplomats point out that until there is control over those as well, a real reduction in arms will be unattainable.

Delamare was the second foreign ambassador to lose his life since the beginning of the Lebanses civil war in 1975.

His ambush was almost at the same place where then-U.S. ambassador to Lebanon Francis E. Meloy Jr., his economic counselor, Robert O. Waring, and their chauffer were kidnaped, June 16, 1976, as the ambassador sought to drive to East Beirut to present his credentials to Lebanon's president. All three men were later found shot to death.