FOR more than 40 years the world has been trying, and failing, to bring all the sides in the Middle East conflict together. Now, with regional fighting in Central America, Southern Africa, and Southeast Asia steadily subsiding, comes a supreme challenge for international diplomacy: a Middle East peace conference.The talks opening Oct. 30 in Madrid between Israel and its Arab neighbors are the first of their kind. An early effort to bring the parties together in 1949 failed to get beyond the stage of indirect discussions. And the Geneva peace conference in 1973 collapsed when Syria failed to turn up. No other peace initiative has even gotten as far as the negotiating table, and only the Camp David accord, a bilateral peace treaty between Israel and Egypt, stands as an achievement. But most diplomats and political analysts with expertise in the region, and indeed most ordinary Arabs and Israelis, see little chance that the conference will lead anywhere. The positions of the countries at war are too far apart and too deeply entrenched to admit peaceful conciliation, runs the accepted wisdom. But there are some signs that permit optimists to keep their hopes alive and that at least help to explain how United States Secretary of State James Baker III has succeeded where so many of his predecessors have failed - in his admittedly modest goal of sitting all the enemies down in the same room at the same time. Fundamental to the success of his mission so far has been the collapse of the Soviet Union as a superpower and the consequent emergence of the US as the only country in the world with global interests and sufficient force to defend them. The new pattern of international relations now taking shape as a result of these developments has naturally had a major impact on the Middle East. At the procedural level alone, an international conference has never been possible because Washington always refused a role to the Soviet Union, frustrating a central Arab demand. Now that Moscow is effectively powerless to implement its traditional Middle East policy, however, its presence as a cosponsor of the conference satisfies the Arab need while posing no threat to US goals. At a deeper level, though, the new global balance of power makes it infinitely easier for the US to impose a "Pax Americana" where conflicts endanger US interests, as the outcome of Iraq's invasion of Kuwait made clear. The Gulf war, as the opening Middle East salvo in President Bush's campaign for his vision of a "new world order," taught lessons to the countries of the region and catalyzed some striking realignments among them. First, Israel played no role in the conduct of the war, proving a liability to US policy as Washington sought to hold its Arab coalition together. "The US has a number of friends and allies in the region now," says Gabriel Sheffer, an expert on US-Israel relations at Jerusalem's Hebrew University. "This is a marked change, and Israel is not anymore an important strategic asset for the Americans." With the cold war over and the traditional US-Israeli vs. Soviet-Arab lineup an anachronism, Israeli leaders are being forced to rethink their attitude. "They know exactly the face of the new age," says Saeb Erekat, a member of the Palestinian delegation at the conference. "The Americans want stability in the region," Erekat argues. "They know that stability means a solution to the Palestinian problem, and that means that the main obstacle to Bush's new order in the Middle East is Israel and the Shamir government." At the same time Arab leaders around the region are also reconsidering their futures, and their conclusions have brought them to a new level of moderation vis-a-vis Israel and the West. There has been no clearer illustration of this change than Syria's role as an anchor of the US-led coalition against Iraq earlier this year, ending decades of vitriolic rhetoric and violence against the West from Damascus. Syrian President Hafez al-Assad appears to have set his price for that cooperation: the return of the Golan Heights, which Israel seized in the 1967 Arab-Israeli war. The Palestinians meanwhile have found themselves vulnerable as a result of recent international events. "We are all the time leaning on the USSR and on the Arab countries," explains leading Palestinian journalist Ziad Ali Abu Zayyad. "Suddenly people discovered that Moscow was a paper tiger and that radical Arab countries were crawling on their hands and knees, with the only real Arab power [Iraq] destroyed.... All this makes people wonder why we Palestinians should be the only blind people in the world." With their international standing undermined by their support for Iraq during the Gulf war, the Palestinians have been left with few cards to play and heavily reliant on the US to squeeze concessions out of Israel. At the same time, the fear among most Palestinian leaders that they will never have another chance to win some sort of self-determination for their people has made them unprecedentedly flexible in accepting the terms of negotiations. "Bush is the ruler of the world," says a top aide to Palestinian Liberation Organization leader Yasser Arafat recently. "Who dares to defy him?" Freed of its overriding rivalry with the Soviet Union, the US has also found it is able - and obliged - to project a new image in its Middle East policy. As the world's only superpower it is forced to adopt a more even-handed approach if it is to convince all parties that it can be an honest broker rather than only Israel's patron. Some analysts see Bush's high standing in public-opinion polls as another important new factor in the Middle East peace equation, if he can afford to keep his eye fixed on the issue. "All previous American initiatives came to nothing because Israeli leaders knew that if they dug in their heels the American attention span is the length of a TV commercial," says Israeli political journalist Peretz Kidron. After eight months of continuous diplomatic efforts, "Bush is a totally new experience for them." If Washington does hold its focus, the negotiations will make clear how strong the US will for peace is, and whether that will alone is sufficient. For if it is fear of angering the Americans that has brought the parties to the negotiating table, the real question is whether that fear can also act as a catalyst for them to find, for the first time, that their own reasons for making peace are stronger than their reasons for making war.