The leaders of the Atlantic Alliance, trying to smooth out two years of U.S.-European differences over how to approach the Soviet Union, issued a broadly worded statement of principles today reaffirming both a strong defense and continued detente.

Even before the ink was dry on the final communique, however, President Reagan warned his NATO partners that he would not accept any detente if it turned out to be a "one-way street."

Speaking in the final minutes of a closed session of the North Atlantic Treaty Organization, the president declared that he was "deeply disappointed" by the "detente of the 1970s," which he said had allowed a Soviet military buildup while Western nations were promoting peace. The remarks were relayed to reporters by White House officials, who said they were praised by NATO Secretary General Joseph Luns but drew no comment from representatives of other nations.

From the administration point of view the president's concluding comments were intended to define rather than undermine the NATO communique issued today, which reaffirmed commitment to "genuine detente." But they also demonstrated the depth of Reagan's suspicions about the Soviets, whom he alternatively has denounced and invited to negotiate during his 10-day European trip.

"Genuine" was added as at the insistence of the Reagan administration, which made insertion of the adjective a condition of mentioning "detente" at all. The key passage read: "Our purpose is to develop substantial and balanced East-West relations aimed at genuine detente."

On the whole, the United States came closer to its objectives today than it did last Sunday in the vaguely worded communique issued by the seven-nation economic summit in Versailles. But the independent-minded Canadian prime minister, Pierre Trudeau, denounced the day's creation as essentially meaningless.

"I don't think that this type of summit can be very productice," Trudeau said. "I think they the NATO leaders should be expected to do more than rubber-stamp a communique whose results have been pre-cooked."

Trudeau said this process was inevitable because the leaders of 16 nations with different views were given only five hours to consider a communique dealing with many complex questions.

The communique issued today, which is likely to become known as the Bonn Declaration, represents a patchwork of compromises and tradeoffs between the United States and its major allies in Western Europe. As is customary with such documents, it was praised by representatives of the different nations as a satisfactory consensus of conflicting views.

The NATO leaders actually approved three documents today--the general communique and separate statements on arms control and defense.

While the arms-control statement endorsed Reagan initiatives, the defense document gave the United States much less than the Reagan administration had sought.

The United States had wanted NATO leaders to reaffirm a four-year-old commitment to a 3 percent annual increase in real spending for conventional forces. Instead, the document pledged to "fulfill to the greatest extent possible the NATO force goals for the next six years, including measures to improve the readiness of the standing forces and the readiness and mobilization capability of reserve forces."

But the document on arms control and disarmament backed the strategic-arms reduction talks sought by the Reagan administration that will begin in Geneva later this month as well as the president's so-called "zero option" of last year to eliminate U.S. and Soviet intermediate-range, land-based missiles in Europe.

This proposal, the statement said, "holds promise for an equitable outcome and enhanced security for all."

Reagan also was said to have been pleased by the statement of French Prime Minister Pierre Mauroy, who strongly backed the U.S. arms-control proposals in a speech today.

Saying that "peace cannot be the result of weakness," Mauroy spoke of the necessity of the U.S. nuclear guarantee, which he said most Europeans supported.

"In particular, we should convince those Europeans who doubt it--which is not the case of France--that intermediate-range nuclear weapons of which the installation has not been decided [the U.S. cruise and Pershing missiles] will not be there to conduct a limited nuclear war in Europe, but, quite to the contrary, to make the adversary understand that a limited war is impossible."

The formal, eight-point communique hailed the admission today of Spain as the 16th member of NATO, saying that Spain's "peaceful change to parliamentary democracy bears witness to the vitality of the alliance as a force for peace and freedom."

Other points in the communique contrasted the freedom of the Atlantic partners--"none dominant and none dominated"--with the "rigid and imposed system" of the Warsaw Pact nations headed by the Soviet Union.

The allies also pledged support to a "stable balance of forces," assistance to underdeveloped nations, "economic and social stability" and opposition to terrorism. "Our purpose is to develop substantial and balanced East-West relations aimed at genuine detente."

In the defense document, NATO leaders showed a growing recognition of Europe's increased vulnerability to the Soviet Bloc resulting from expanded U.S. defense commitments around the world. The document recognized that the deployment of forces to other regions by NATO countries, such as the U.S. Rapid Deployment Force in the Persian Gulf, "can represent an important contribution to Western security."

The summit host, West German Chancellor Helmut Schmidt, took the final statement as a reaffirmation of a balanced Western alliance policy, noting that the two-track approach to the Warsaw Pact of defense coupled with detente dates back to the so-called Harmel Report NATO accepted in 1967.

He told reporters later that he was satisfied that the conference had contributed to "consensus within the alliance" and said there was agreement between West Germany and the United States "in the direction of an active peace policy."

Washington Post correspondent Bradley Graham contributed to this report. PHOTO(AP): Peace demonstrators jam the streets of downtown Bonn during the summit meeting of NATO leaders. Among the signs is one that calls for Europe free of atomic weapons.