The massacre of Palestinian civilians by Lebanese Christians following Israel's invasion of west Beirut has left the US star on the wane in the Middle East.
Israel's latest advance into west Beirut despite objections by the United States has caused US credibility to plummet in Arab capitals.
Such a credibility gap will make it far more difficult - if not impossible - to attract moderate Arabs, especially Jordan, into peace negotiations. Moreover, the events in west Beirut may also push the Palestine Liberation Organization, whose tacit acquiescence is needed at minimum for Palestinian participation in any new peace moves, away from any compromises.
Israel has never before occupied an Arab capital. It was fear of such an occurrence that spurred Arab states like Saudi Arabia to pressure the PLO to leave Beirut. Israeli assurances to the US that Israel would not enter west Beirut were critical in obtaining Lebanese government and PLO acquiescence to the plan for the PLO's evacuation.
Thus, Israel's move has been met with cries of outrage from many Lebanese officials.
''I consider what happened a scandal especially since we had American guarantees personally from President Reagan and in written form from Secretary (of State George) Shultz that west Beirut and its inhabitants would be safe after the PLO withdrawal,'' Lebanese Minister of Tourism Marwan Hamadeh told the Monitor.
PLO chairman Yasser Arafat, who watched American network video footage of the massacre with key PLO leaders in Damascus, charged that the multinational force of US, Italian, and French troops which supervised the PLO evacuation failed in its duty. He said the PLO had been assured that Palestinians remaining in Beirut would be protected from revenge-bent Christian Lebanese after the PLO left. The fact that US Marines left Beirut early before their mandate expired is seen by PLO figures as proof that the US knew what was about to happen.
Several prominent Jordanian officials told the Monitor that they believed Israel launched its invasion of west Beirut, specifically to undermine the Reagan initiative. King Hussein of Jordan, who had been the most enthusiastic of any Arab leader about the plan, called on the US to move immediately to end ''Israeli aggression in west Beirut'' because the Israeli attacks aimed at ''harming the US reputation and image in a the Arab world'' at this critical time.
It is hard to find a prominent Arab or Palestinian figure in Damascus, Amman, or Beirut who does not believe the US knew in advance of Israel's move into west Beirut, an allegation boosted by statements by Israeli Defense Minister Ariel Sharon. Such beliefs undermine the sharply positive impact the Reagan initiative made on Arab moderates only two weeks ago.
The attraction of the Reagan plan was its clear definition - for the first time - of an American position on the Palestinian problem that indicated US willingness to challenge Israeli opposition to returning the occupied West Bank and Gaza Strip to Arab sovereignty.
But moderate Arabs, including Jordan, remained skeptical of US willpower to challenge Israel's rejection of the plan. This skepticism was magnified by Israel's approval of new Jewish settlements on the occupied West Bank immediately after President Reagan's call for a freeze on such settlements. Such issues were about to be explored in an Arab-US dialogue following the Fez Arab summit.
Now that Israel has defied a unanimous Security Council vote to withdraw from west Beirut, Jordan and other moderate Arab states will be watching closely to see if Israel can flaunt US wishes with impunity. If they conclude this is the case, it will be far, far harder to attract them to the negotiating table.
As for the PLO, the Israeli invasion of west Beirut and the west Beirut massacres may tip the organization away from an expected new emphasis on pursuit of the political option.
''Before west Beirut things were different,'' said one PLO official in Damascus. ''Now all those in the PLO who maybe thought that there was something serious in the Reagan proposals - and they were few - are changing their minds.''
The PLO Central Committee was meeting in Damascus Sunday to discuss events before convening the Palestinian parliament or national council. Chairman Arafat , will soon have to decide where to base himself and his entourage. All other major PLO leaders have settled in Damascus, but relations between the PLO chairman and Syria's President Hafez Assad are strained. They did not shake hands at the Fez summit. The PLO leader arrived in the early morning hours to Damascus airport in an apparent attempt to downplay the significance of his first trip to Damascus since being evacuated from Beirut.
But Palestinian sources here say that in coming months the PLO leader may be impelled by events in Beirut to spend more time in Damascus and to focus on military moves rather than on diplomacy. They now expect that Israel will remain for some time in Lebanon. This means Syrian and PLO troops will stay put in the Bekaa Valley and in north Lebanon. This, they say, will inevitably lead to clashes with the Israelis and perhaps to major battles.