Far from troubled Beirut in the relative peace of this southern Lebanese village sits a burly red-bearded man who is deeply worried by last week's fighting between Syrian peacekeeping troops and rightwing Christian militiamen.

He is also one of the reasons behind it. And now, with Israeli and Syrian troops threatening to face off because of the Beirut fighting, his role is becoming increasingly critical.

Major Sami Shidiak is one of two Christian Lebanese Army officers who allied themselves with Israel in a battle against Palestinian guerrillas and Lebanese Moslem leftists following the 1975-76 civil war. When Israel invaded southern Lebanon last March, he and Maj. Saad Haddad cooperated with the Israeli Army and inherited its key positions when it withdrew last month.

The result has been to stymie the deployment of U.N. peacekeeping forces in the south and rankle the Syrians and Lebanese Moslems in the north. Explaining their artillery attacks last week on Beirut's Christian districts, Syrian sources said Christian rightists were collaborating with Israel and demanded that the Lebanese government dismiss Shidiak and Haddad.

So far, the government has followed its apparent policy of skirting decisions whenever possible to avoid offending anyone. It has not ruled definitively on the status of Shidiak, Haddad and their approximately 700 regulars. Instead, it has given them orders to confine their men to barracks.

Shidiak and Haddad say they have done this, but more than 800 irregular Christian militiamen who have been fighting under them have taken up the task of keeping the U.N. troops and the Palestinians out of their areas.

"The big problem now for me is what's happening in Beirut," said Shidiak as he sipped a can of beer on the balcony in back of his house a few miles north of the Lebanese-Israeli border. "If we feel everything is lost in Beirut, I don't know what we will do." After a pause he said, "I can blow up the whole situation."

He would not elaborate, but an aide explained: "The government must first be able to stop the Syrian Massacre. After that we will see if we are able to execute their orders. We are not the army of anyone. We are the army of our own security."

Officials of the U.N. force in Lebanon express the hope that pressure on the Christian rightists in Beirut will compel their militiamen in the south to concede more positions to the U.N. Force and thus allow it to fulfil its mandate of policing all territory evacuated by Israel.

"The whole scene may change because of what's happening in Beirut," said an Irish officer at U.N. headquarters in Naqoura on the southern Lebanese coast. "They may be looking for us to come in before too long."

But that appeared to be more wishful thinking than anything else. A meeting the same day with Maj. Haddad produced no new U.N. positions, and Maj. Shidiak and his men were still adament about keeping the U.N. out.

"The U.N.? They are useless," Maj. Shidiak snapped as he pitched a beer can over the railing. "They don't want to have a problem with anybody."

Shidiak waved a thick arm at the rolling, rockstrewn hills of which his balcony affords a spectacular view.

"Yesterday we had an accident over there in the village of Srobbine," Shidiak said. He said a militia patrol encountered a band of Palestinian guerrillas and was fired upon with heavy machine guns, losing one man.

"The Palestinians were behind U.N. lines," Shidiak continued. "They had infliltrated. I shot on their position with a cannon and drove them out. Then I sent a letter to the people of the village telling them they must advise us if strangers come there. Or else they will be held responsible and I will fire on them"

Shidiak says his 237 Lebanese army regulars are "not doing military missions" on Beirut's orders. Despite reports that his acceptance of those orders causes friction between him and local Christian rightwing militiamen, however, it was evident that the irregulars are still loyal to him and that he still pulls the strings in his area.

Shidiak's military equipment comes from Israel, he keeps in touch with Israeli officers and his wristwatch is even set on Israeli time.

"Here we have no problems," Shidiak said. "We have Israel behind us. They promised to protect us."

As if to drive home the point, when he waved goodbye to his visitors, his parting word was "Shalom."