Talks between Israeli and Lebanese army officers on how to bring peace to southern Lebanon resumed today - 12 days after Israel suspended negotiations over alleged violations of the Sept. 26 cease-fire by the Palestine Liberation Organization.

A reconstituted Lebanese army is trying to impose its authority in the border region where Christian forces, with considerable help from the Israeli army, have been battling Palestinians for the past year.

So far, the Lebanese army - divided into warring factions during last year's civil war - has not been able to police the area.

The Lebanese officers were flown in a United Nations plane from Beirut to Haifa, according to an Israeli army spokesman, and then driven north to the Israeli border village of Rosh Hannikra where the 2 1/2-hour talks took place.

The reason for the U.N. flight was that the Lebanese officers are still unable to reach the border by road because their control over the area has not yet been re-established. The U.N. flight itself - the only one to connect Beirut directly with Israel - brings into focus the delicate, dangerous, and largely unreported role the U.N. forces are playing in southern Lebanon.

The U.N. observer force - here since 1949 - is so anxious to preserve its impartiality that it shuns any publicity. Nevertheless, the observers, made up of soldiers from 16 different countries have regularly been shot at, shelled, had their vehicles, radios, flak jackets and other equipment stolen at gunpoint and have been otherwise abushed by both sides since the fighting started in the border region a year ago.

The United Nations has lost nearly 60 vehicles to Christian, PLO forces, or just plain bandits in the last year. The latest was a fully equipped vehicle taken at gunpoint by Palestinians yesterday.

Although no one has yet been killed, a British officer nearly lost his leg when his vehicle hit a land mine July 14. According to informed sources, he may never walk again. An American officer was lightly wounded in a similar incident in August.

According to an Associated Press report from Beirut, a French officer was forcibly attacked sexually by six unidentified guerrilla fighter.

Unlike the U.N. forces on the Golan Heights between Israeli and Syrian forces, and in the Sinai between Israeli and Egyptian forces, the U.N. observers in southern Lebanon are unarmed. Perhaps even more frustrating, there is no established authority to complain to, given the near-anarchy of the Lebanese war.

While the U.N. forces are powerless to resist, some U.N. sources believe that the very fact tha the observer troops are known to be unarmed has probably saved them from being murdered.

The guerrillas seldom take personal belongings or money according to knowledgable sources, but they feel free to take any equipment they think they need. Flak jackets are a very popular item and are lifted off the backs of U.N. officers at will. Observations posts are regularly robbed of generators, radios and other equipment.

The only change in pattern recently is that several months ago the U.N. observers seemed to have more trouble with the Palestinians than the Christians but now the situation has been reversed.

Since the Israeli incursion into southern lebanon last month, the Christian will no longer permit U.N. observers to pass through to their posts from the Israeli side, so the U.N. soldiers must come all the way down from Beirut where they are escorted through to their border observation posts by the PLO.

There is speculation that since the Israeli incursion, which resulted in a shaky cease-fire after intense American pressure on the Israel is to withdraw, the Christians no longer want the U.N. units to see how much help they are getting from the Israelis. On the other hand, the PLO, following the Israeli incursions, now finds it in its interest to have some observers around in case the Israelis return.

The Israeli - Lebanese mixed Armistice Commission was established by the United Nations in 1949 following the cessation of hostilities between Lebanon and the newly formed state of Israel. In 1972, the Lebanese government asked the commission to build five observation posts along the border with Israel. The reason for the request was because PLO forces had begun operating in southern Lebanon, following their expulsion from Jordan and were causing armed Israeli retaliations. All through the recent fighting the United Nations has managed to keep its border posts operational despite harassment from both sides, observing a war they have no power or authority to prevent.