WASHINGTON -- The Clinton administration has joined with its European allies and Russia for the first time to forge a detailed, bottom-line peace proposal for Bosnia based on a near-even split of land between the contending forces. Washington had resisted endorsing specific outlines for a territorial solution between a Moslem-Croat federation and a breakaway Serb force. In recent months, however, U.S. officials had approved in principle a 51 percent to 49 percent division of land, with the Moslems and Croats receiving the bare majority. Now Washington is formally supporting that plan, which is scheduled to be presented in Geneva at peace talks scheduled to resume Saturday. Concern that talks between the Bosnian-led Moslem government and the Serbs were going nowhere, and that the war would drag on, prompted Washington to propose the "de-facto map" for partition, with details left to the warring factions to work out, a State Department official said. The plan includes advice on resolving differences over disputed territory in several parts of Bosnia, including the contested Bihac region and isolated Moslem enclaves of east Bosnia. "This is do-or-die for the Moslems, Croats and Serbs," a State Department official said. "We basically offer a solution, but it is up to them to decide whether to accept."There is no indication that either the Moslem-led government or the Serbs will embrace the proposal. The Moslems say they want more than 51 percent and their military leaders believe they can make up ground on the battlefield. The Serbs have shown no sign of giving up any territory. The Serbs now hold more than two-thirds of the country after a two-year war of conquest that has included systematic killing and expulsion of civilians from their homes. The U.S.-backed proposal is based on a combination of solutions bandied about in previous talks, a U.S. official said. U.S. envoy Charles Redman, and mediators from Russia and the European Union -- all in the so-called Bosnian "contact group" -- hammered out the new proposal. Redman is in Europe meeting with mediators from Russia, Britain, France and Germany in advance of Saturday's meeting. The Clinton administration had strongly resisted endorsing a clear territorial solution, especially one ratifying any Serb gains. Washington long based its policy in Bosnia on opposition to the Serb conquest of territory by force. Recently, confusion clouded the Clinton administration stand on the territorial issue. In talks brokered by Redman, the Moslems and Croats based an agreement to form a confederation on a 58 percent to 42 percent split of land, with the Serbs getting the smaller part. At first, Redman hailed the agreement. That prompted the State Department to qualify the endorsement to cover only the Moslem-Croat agreement to unite, not the 58-42 percent division. The coming talks on land were supposed to be preceded by talks beginning Thursday on a cease-fire. But United Nations special envoy Yasushi Akashi postponed the negotiations because the Serbs declined to withdraw 300 soldiers from the Bosnian Moslem town of Gorazde as promised.