BONN, SEPT. 7 -- West German Chancellor Helmut Kohl has invited President Bush and Soviet President Mikhail Gorbachev to shake hands at the former site of the Berlin Wall, ushering in the reunification of the two Germanys with a ceremony formally ending the Cold War.

Both Bush and Gorbachev appear interested in attending the celebration of German unity Oct. 3, and both leaders have agreed to talk to Kohl about the idea next week. Kohl's spokesman said today that the Germans will also invite British Prime Minister Margaret Thatcher and French President Francois Mitterrand to attend the symbolic event, at which the flags of the two Germanys and the four World War II powers are to fly over Berlin's Brandenburg Gate.

The two Germanys have declared Oct. 3 a national holiday. Workplaces and schools will be closed, special church services held, speeches made and the first meeting of the joint German parliament convened.

The Bonn government is working furiously to plan the nationwide party marking the return of full sovereignty to the nation that emerged from World War II defeated and divided. But even as plans for the big day continue, diplomats are struggling to complete two sets of negotiations clearing the way for a unification that was inconceivable a year ago.

Wednesday, the foreign ministers of the two Germanys and the four victorious World War II powers are scheduled to meet in Moscow to sign a document ending foreign legal rights in Germany.

And West German and Soviet negotiators are working long days toward completing an agreement on Bonn's offer to pay much of the cost of the 360,000 Soviet troops still stationed in East Germany. The Soviets have agreed to pull out of German territory during the next three to four years; in exchange, Bonn has promised to pay some of the cost of the troops' continued presence in East Germany, as well as part of the cost of transporting the troops home and even building housing for them in the Soviet Union.

Today's session in the Niederschoenhausen Castle in East Berlin to prepare for the six-nation agreement ended with most, but not all, of the remaining issues resolved. West German and U.S. diplomats said that the few questions still lacking answers are not crucial enough to threaten next Wednesday's scheduled completion of the talks.

Before they agree to give up legal responsibility for the country that until last fall was the forward pillar of the Warsaw Pact, the Soviets want assurances that neither the united Germany nor NATO will station nuclear weapons or nuclear-capable artillery on the land that was East Germany.

But the Western allies have refused to make that commitment, arguing that making eastern Germany a nuclear-free zone would infringe on the sovereignty of a united Germany. The West German government independently has announced its intention to remain a non-nuclear power, although U.S. nuclear warheads are stationed in West Germany.

The six foreign ministers are expected to resolve the remaining issues in Moscow on Tuesday, before the signing ceremony Wednesday.

The German-Soviet talks in Bonn have gone less smoothly. Negotiations bogged down this week as the Soviets demanded 10 billion marks (about $6.5 billion) to cover the costs of keeping its troops in East Germany.

The Soviets want Bonn to agree to pay not only for the transport of the soldiers out of Germany, but for their food, electricity and other supplies during their remaining stay. Soviet negotiator Stepan Sitaryan, Moscow's deputy prime minister, asked for another 10 billion marks to build housing for returning Soviet soldiers and their families. The Soviets also want Germany to retrain soldiers and to reimburse Moscow for the property it controls in East Germany.

West German Finance Minister Theo Waigel called the latest Soviet demands "unrealistic" but reiterated Bonn's commitment to pay some portion of the cost of building housing. Bonn already has paid almost $700 million for the maintenance of the Soviet presence in the past six months.

A Bonn official called the Soviets' last-minute demands "a typical Soviet act of brinksmanship." Said one U.S. diplomat: "This is the Soviets' time of maximum leverage. They know the Germans are committed to reunifying on Oct. 3, and they are trying to get the most money possible before then."

Bonn officials said the German-Soviet pact is nearly finished except for the amount Bonn will pay for troop stationing.