France has shifted gears from its direct opposition to the Bush administration's plans for a National Missile Defense system, joining Germany and Britain, for the time being, in willingness to consult with the United States about the project.

This means that the administration probably has 18 months to two years in which it can operate in developing the program without the risk of its becoming a major source of dissension within the Atlantic alliance. It also signifies that until the United States lays out the specific architecture of the plan, the Americans probably have succeeded in avoiding active opposition to it beyond the expected sources in Russia and China.

The defense system, which the United States maintains can protect it and its allies from attacks by so-called rogue states without great disruption to existing arms control agreements, is still in an early, conceptual stage.

Britain has said that it considers a missile defense achievable. Germany, after initially expressing opposition, has moved off that position to accepting as a fait accompli the United States' intention to go ahead with the plan, and is now asking questions about the possibility of participation in the missile shield's industrial development. .Last month, President Jacques Chirac described France as "enormously" concerned about the U.S. plan, saying that it was certain to incite nuclear proliferation, create strong international tensions and result in vast costs.

The undertaking, he said, "to us hardly seems a priority for responsible men with a certain vision of the future." .But none of that tone was evident when Foreign Minister Hubert Vedrine, in response to a reporter's question after a meeting Thursday night with Foreign Minister Joschka Fischer of Germany, described the current French view.

Rather, Mr. Vedrine adopted an almost nonjudgmental vocabulary. "France and Germany," he said, "have expressed questions. It's a bit difficult to be very precise in making an analysis because we don't know what" the U.S. plan consists of. He added: "What's important is that consultations begin. We've remarked that Secretary of State Powell has started discussions with NATO and Russia."

The French recalibration reflects the observation here, acknowledged privately by a French official, that neither Germany nor Britain, however skeptical they may be about the missile shield and its policy implications, wants to do battle on the issue.

For France, the missile shield, if extended to U.S. allies, would raise existential questions about the value of its own nuclear deterrent, while increasing Europe's dependence on the United States. But for the time being, the French, well after the Germans and the British, appear to have reasoned that aggressively opposing the shield means more loss than gain.

For one, an opposition stance parallel to that of Russia at a time when the French have invested heavily in smooth movement toward construction of a European pillar in the North Atlantic Treaty Organization could only irritate their alliance allies and European Union partners.

As important to France, the change in tone means moving its position on an essential strategic issue to a point less obviously out of step with that of Germany.

This comes at juncture when it is making great efforts to convince the Germans that there is energy and utility left in the French-German tandem, once called the motor of European progress but now referred to by Mr. Fischer as its "flywheel," an object whose purpose, as defined by Webster's, is "opposing and moderating by its inertia any fluctuation of speed in the machinery with which it revolves."

U.S. Assures Allies on Defense .The United States has assured its allies that it will help them develop defenses against long- and short-range missiles and said President George W. Bush will visit NATO headquarters in Brussels in June, Reuters reported from Washington.

The NATO secretary-general, George Robertson, held separate talks Thursday with Mr. Bush and Defense Secretary Donald Rumsfeld that appeared aimed at reassuring Europeans who are worried over Mr. Bush's plan for a National Missile Defense.

Mr. Rumsfeld also met the German defense minister, Rudolf Scharping, who said there was agreement, including in Moscow, that there was a new threat and that missile defense should be part of a "long-term and comprehensive" strategy against it. But, speaking to reporters, he said that any missile defense system must be integrated into NATO's overall "Strategic Concept" agreed two years ago at a Washington summit meeting that enshrined the need for arms control and reduction.

"It is a question of confidence within NATO, and question of credibility in international affairs, that this is not only rhetoric," Mr. Scharping said. Talks on missile defense must be accompanied by talks on deep cuts in nuclear weapons, he said. Mr. Rumsfeld, speaking at a joint Pentagon news conference with Mr. Robertson that "theater" defense against short-range attack was as important to many nations as a shield against long-range missiles was to the United States.

"What's 'national' depends on where you live, and what's 'theater' depends on where you live," he added, addressing concerns in Europe and elsewhere that a successful long-range defense for the United States could leave allies vulnerable.

Mr. Robertson later met Mr. Bush at the White House. The National Security Council spokeswoman, Mary Ellen Countryman, said they discussed NATO enlargement, NATO's missions in the Balkans and "NATO's role in building a Europe whole, free and secure."

They also discussed missile defense, noting Russia's recent "conceptual concession that defense systems should play a role in countering the threats of the new security environment," Ms. Countryman said. And they talked about European plans for a defense force. Mr. Bush, as he did in a meeting with Prime Minister Tony Blair of Britain two weeks ago, said he would favor the force as long as it did not undermine NATO.