LONDON, JULY 6 -- President Bush today advanced his administration's urgent foreign policy goals of bolstering besieged Soviet President Mikhail Gorbachev and speeding the unification of Germany by getting America's European allies to endorse a new vision of European defense that eventually will reduce the role of American troops and nuclear weapons on the continent.

The president's success at the NATO summit here was not total. His new doctrine of using nuclear weapons in Europe only as a "last resort" was included in the final communique, but it was immediately disavowed by the only two other nuclear powers in NATO. The disavowal by France's President Francois Mitterrand was explicit, while Britain's Prime Minister Margaret Thatcher made her objections implicitly but clearly.

The summit produced a surprise breakthrough in West Germany's willingness to accept limits on German troop levels after unification of East and West Germany. That willingness may resolve one of the Soviets' biggest worries about a united Germany becoming a full member of NATO. "The Soviets have repeatedly identified an assurance on German troop levels" as a major requirement and Bonn has now put one forward, a U.S. official said.

The new German position on troop levels -- and Bush's willingness to go along with it -- was singled out by the official as perhaps the most important result of the summit because of its likely impact on Soviet concerns about unification.

At times in the two-day summit, Bush found himself racing to keep up with the West Germans in pulling the 16-nation alliance into a future beyond the containment of a hostile Soviet Union in a divided and vulnerable Europe. Eager to protect the chances of German unification, the Bonn government pushed ahead in promising limits on security levels and promoting a stronger Soviet-German relationship than the president appeared to have expected.

At other times, he struggled to bring along Thatcher and Mitterrand, who dug in their heels on some key points and in general suggested that they preferred a status quo that they realized was being changed before them.

But at his summit-ending press conference, Bush seemed pleased that the verbal tug of war produced a final declaration that retained the major departures in NATO strategy and doctrine that he had proposed in a draft declaration circulated to other delegation leaders last week.

Bush even urged Gorbachev to take credit for having created the conditions that led to the dramatic changes spelled out in the 23-paragraph document and to use them as ammunition against hard-liners who are trying to slow down arms control accords with the United States and the unification of East and West Germany.

"If I were him, I'd say, 'I've been right,' " Bush said, acknowledging that one of his primary goals here had been to change NATO's image in the eyes of the Soviet leadership and people. NATO is changing "because of steps I have taken," the president imagined the Soviet leader saying to the hard-liners after reading the communique.

The Soviets strongly and consistently have objected to the "flexible response" doctrine, which implied that the NATO alliance would use nuclear weapons first and fairly early to blunt a massive Soviet conventional assault. Those objections persuaded Bush that dropping that term and stating a commitment here to make nuclear arms "weapons of last resort" would help Gorbachev in his internal battles and make him more forthcoming on German unification and other security issues, one U.S. official confirmed.

"This is a signal, albeit vaguely stated, that there has been a substantial change in our attitude toward nuclear weapons. It is a recognition that in the rapidly changing security situation in which there will be conventional parity and the Soviets will no longer be in Eastern Europe, flexible response was simply not credible any more," the official said.

But in closed-door arguments with Bush, Thatcher and Mitterrand said that any shift in deterrence philosophy at this point was unhealthy.

"Deterrence is to prevent war, not to win a war. Suggestions that there are degrees in the use of nuclear artillery and other weapons or that a war {in Europe} would be a long process that can be regulated like a music score is totally contrary to reality," said Mitterrand, who added that France would not be bound by the decision. "We do not share the concept of last resort."

France, although a member of NATO's political structure, does not belong to the alliance's integrated military command.

Thatcher stated her objections by twice reading language she had inserted in the communique, stating that nuclear weapons still play "an essential role" and that "there are no circumstances in which nuclear retaliation in response to military action might be discounted."

But West German Chancellor Helmut Kohl hailed the shift in strategy and praised Bush for deciding not to modernize short-range nuclear missiles and offering to pull U.S. nuclear artillery shells out of Europe.

Kohl was ebullient about the changes adopted here, saying that at NATO's last summit in May 1989, "we did a risk assessment. Now we're working out a strategy. . . . This coming decade will be the decade of Europe."

Even more striking than any statements made by the West Germans on economic aid to the Soviets was Bush's uncomplaining acceptance of Bonn's right to provide any amount and any kind of financial assistance to Moscow that it wants. Bush's emphasis on the fact that he had never even thought of suggesting to Bonn that it hold back on aiding the Soviets carried a hint that he doubted that such a suggestion would have been honored.

"The Germans have their own bilateral relationship with the Soviet Union, and it doesn't concern me one bit," Bush said at one point in his press conference. "I've not made one single effort to try to have the Germans look differently at that question."

U.S. officials said that while Bush continues to doubt the political and economic wisdom of joint financial aid from the West to the Soviets, he may be prepared at the Houston summit of the Group of Seven industrial powers next week to agree to study such an idea.

Bush entered the NATO meeting hoping it would produce a document that would provide a political rationale for keeping American forces in Europe but at a greatly reduced level. By calling for NATO to "field smaller and restructured active forces" and to "rely increasingly on multinational corps made up of national units," the final communique went a long way toward meeting Bush's goal.