A diplomatic logjam needs to be broken if western Beirut is to be spared widespread destruction.
Which of the many antagonistic parties to the conflict in Lebanon will make a concession? Who can offer a new approach?
Israeli and Lebanese Christian Phalange officials June 29 refused to accept the concept of any armed Palestinians remaining in Lebanon, even if they were attached to the Lebanese Army. Israel said the only option the Palestine Liberation Organization had was to drop all weapons and leave the country, by sea or through Israeli Army lines to Damascus, Syria.
The PLO's Yasser Arafat and at least some members of the Lebanese Cabinet are drawing up a plan to ''reorganize'' the PLO forces in Lebanon. The proposal subjects the PLO to the Lebanese central government and calls for redeploying partly in the Bekaa Valley and partly in the northern region around Tripoli. It also calls on the PLO to generally be on its best behavior.
But nowhere in Beirut were there negotiations concerning Palestinian disarmament and flight from the country. Thus, Israel and the PLO are not talking about the same thing.
''The PLO completely rejects the idea of laying down arms, rejects Israeli conditions calling on us to leave,'' Bassam Abu Sherif of the Popular Front for the Liberation of Palestine told the Monitor. Mr. Abu Sherif added, ''We think Begin and Sharon (Israeli Prime Minister Menachem Begin and Defense Minister Ariel Sharon) are angry and are looking for a chance to strike west Beirut. We think the military option is 60 percent at least.''
This ''military option'' seemed to loom large June 29, outside options being minimal. In quick succession there have been reports that Egypt was sending ships to rescue PLO leaders and that Saudi Arabia was sending planes for the same reason. But little has come of these reports. In fact, grim as it seemed, Beirut June 29 appeared to be waiting for the shooting to start.
Streets in west Beirut were uncharacter-istically deserted. Shops were shuttered, apartments abandoned. Many more young men with machine guns were sauntering around the commerical district than ever before. Outside the city, Israeli forces continued to position tanks and armored personnel carriers outside Palestinian camps. West Beirutis fretted over every scattered boom or bang, wondering if the four-day cease-fire was about to end.
With diplomacy at an impasse, all that seemed to be delaying a final battle for Beirut was Israel's tallying of pluses and minuses. They are understood to be the following:
* First and foremost, Israeli casualties. Street fighting throughout the capital would cause high numbers of Israeli casualties and thus could hurt Messrs. Begin and Sharon politically.
* Reagan administration reaction. Mr. Begin is believed to have promised President Reagan that Israel would try to refrain from attacking Beirut. The destruction and loss of life that would come with an Israeli assault could be damaging to Israel's relations with the United States and Western Europe, especially if Arab countries retaliate, perhaps by halting oil sales to the West.
* But hostile Arab reaction could actually work in Israel's favor by the convoluted logic of the Middle East. A PLO official points out that if Arab states used the oil weapon or broke diplomatic relations with the US, Israel could again promote itself as the only friend America has in the Middle East.
* Moreover, despite the difficulty of the street fighting, Israel would no doubt win in the end. That would mean, to the Begin government, credit for the destruction of the PLO. And it could be offered to the West as the destruction of terrorist havens for not only Palestinian groups but also the Armenian Secret Army, the Red Brigades, the Red Army, and assorted other revolutionary movements throughout the world.
''We can't stop them from destroying our camps and killing thousands of people,'' Mr. Abu Sherif admits. ''But we can promise that the price will be high. The PLO leadership does not consider the battle of Beirut as the last battle, any more than the battles of Tyre and Sidon and Damour were our last battles. We are in a state of war with the Israelis and that will continue.''
Both Israel and the PLO, it seems, were girding for war. The diplomatic dance that has been going on the past few weeks and was continuing June 29 so far has been of little consequence, except to buy time for Lebanese civilians to get out of west Beirut.
Diplomacy also helps set the historical record straight, showing that all sides tried to be reasonable before the shooting began.
But statements referring to ''neo-Nazis in Tel Aviv'' and Palestinian ''terrorists'' continue to be issued.