BERLIN, AUG. 20 -- West German Chancellor Helmut Kohl, torn between his desire to please his American ally and his reluctance to break with 40 years of tight restrictions on German military activity, today failed to unite his government in support of sending German troops to the Persian Gulf.

Kohl met with members of his ruling coalition and later with opposition leaders, but was unable to garner support for joining the U.N. peace-keeping troops in the gulf or reach a consensus on a quick change of the constitution, which appears to restrict the use of German force.

In the last four days, U.S. diplomats at NATO headquarters in Brussels have stepped up pressure on Western European nations, particularly on West Germany, to back the U.S. presence in the gulf with more than words.

Sources in Brussels said that President Bush is urgently seeking a deeper commitment to the gulf military mission than nations other than Britain have provided up to now. The message coming from Washington is that if the Europeans' tentative response to the gulf situation continues, it would strain the NATO alliance and make it more difficult for the Bush administration to find broad support in Congress for the gulf mission.

Kohl is said to believe that German forces should be sent to the gulf, in appreciation for Bush's strong support for German reunification. But after meeting for several hours with Foreign Minister Hans-Dietrich Genscher and Defense Minister Gerhard Stoltenberg, Kohl made it known that immediate German military action is now considered impossible.

According to some constitutional lawyers, Bonn is forbidden from sending its Bundeswehr -- now the largest military force in Europe after the Soviet Union's forces -- outside NATO territory. Other lawyers argue that the constitutional restriction is not that clear.

Bonn has given the United States permission to use American bases in West Germany to transport troops and materials to the gulf region, and has sent minesweepers to the Mediterranean Sea to replace U.S. forces deployed to the gulf.

Bonn's Defense Ministry also announced today that it will lend the United States 10 tanks designed to detect poisonous gas. The Pentagon ordered 10 German-made tanks, but since they are not ready for delivery, Bonn agreed to send 10 of their own vehicles.

But Genscher maintained today that no further German role is possible without a constitutional change.

Opposition leader Oskar Lafontaine, the Social Democratic challenger to Kohl in his reelection bid this fall, said there is "no reason" to rush to amend the constitution.

Social Democratic parliamentary leader Karsten Voigt was also against revising the constitution and said no change should be made unless East Germans are represented in the decision.

Therefore, Lafontaine said, new guidelines for the German military can be created only after the two Germanys unify, a move now expected sometime next month.

The nine nations of the West European Union meet in Paris Tuesday to consider sending a joint task force to the gulf. West Germany is expected to support such a move, but only if the force is created without requiring German troops to participate.