Western European nations formally launched their Middle East peace probe today, directing the president of the European Economic Community to contact Palestine Liberation Organization chief Yasser Arafat and leaders of eight Middle East nations.

The mission is part of Western Europe's bid to play a greater role in the peacemaking process -- a move that threatens to put the allies at further odds with Washington.

But Western European officials sought to downplay any friction with Washington, saying that the purpose of their initiative was chiefly to explain to Arabs and Israelis the meaning of the declaration on the Middle East issued by Common Market leaders in Venice last month and to sound them out on a wide rauge of issues.

Gaston Thorn, the prime minister of Luxembourg who as the current Common Market president will be making the tour, labeled it an "information" and "contract" mission.

"The mission is intended to make a contribution to restoring peace in this area of the world and to live up to our responsibilities," he told a press conference.

In their Venice statements, the Western European leaders tilted away from the United States and Israel and toward the Arab camp, publicly endorsing the right of Palestianians to self-determination and calling for the involvement of the PLO in the peace talks. The compromise declaration upset both the Israelis and the Arabs, although it assuaged Washington's worries that the European allies would injure the Camp David peace process by going so far as to propose a new U.N. resolution on the Middle East.

The possibility the Europeans would try something at the United Nations flickered briefly here again today at a meeting of Western European foreign ministers. The West Germans pressed the other Europeans to back a U.N. resolution based on th e Venice declaration.

The surprise West German move seemed odd on two counts: First, Bonn has resisted taking a leading role on Middle East affairs within the Western European community in the past and secondly, the West Germans have shown some reluctance to interfere with Washington on Middle East peace policy.

According to West German officials Bonn's purpose was to try to avert a head-on clash between the United States and Arab countries during a special session of the U.N. General Assembly, which began today in New York, Arab countries asked for this session to generate an international consensus for prompt Israeli withdrawal from all occupied Arab lands.

The West German motion was rejected by other council members as potentially doing more harm than good by antagonizing both the Arabs and Americans and jeopardizing Thorn's mission.

In their mandate to Thorn, the Western European foreign ministers outlined four central questions to be asked of Middle Eastern leaders:

How to implement the rights of Palestinian self-determination.

How to ensure the long-term security of Israel.

How to ensure the participation of Palestinians in the peace negotiations.

What other conditions and perspectives should be considered for the negotiations.

Just what the Europeans will do with the answers to these questions remains uncertain. Thorn's findings could form the basis of a more ambitious initiative by the Western Europeans, possibly including an attempt to secure changes in current U.N. resolutions so as to give explicit recognition to the rights of the Palestinians.