The Reagan administration, while saying it will consult allies about the Warsaw Pact's proposal for a nonaggression agreement with NATO, virtually dismissed the offer yesterday as a restatement of old ideas previously rejected by the West.

"At first blush, we do not see anything new in it," State Department spokesman John Hughes said after reading a detailed statement elaborating on President Reagan's remarks at his news conference Wednesday.

Reagan, answering questions shortly after the first details of the Warsaw Pact offer became known here, replied, "This is something, I think, certainly to be considered." He added, though, that the proposal "has just happened . . . and would require consultation with all of our allies in NATO."

"Peace with justice must always be this nation's highest priority," Hughes said. "We are, and will continue to be, receptive to ideas which would genuinely promote peace and peaceful settlements of disputes. Our discussions with our allies will consider whether this is such a proposal."

He added, "At first glance, it does not seem to represent anything new. But as the president said, we will look at it. We learned from bitter experience between the two World Wars that simple declarations of peaceful intent are not enough. What we need are concrete results, which not only reduce the danger of war, but which contribute to an atmosphere of increased trust."

Other U.S. officials, after studying the details of the Warsaw Pact offer that were made public yesterday, described the proposal as a compendium of ideas the Soviet Union has been putting forward for years.

The West has rejected them as meaningless or designed to enhance Moscow's strategic and political position within Europe.

In particular, the officials noted, the Warsaw Pact declaration states that "the core" of the proposed treaty calls for NATO and pact members not to be the first to use either nuclear or conventional weapons against each other.

The officials said this is a variation of the Soviet declaration to a U.N. disarmament conference last June that it was forswearing first use of nuclear arms and challenged others to do the same.

At the time, the United States and its allies dismissed the idea as a Soviet attempt to score propaganda points amid U.S.-Soviet talks on reducing nuclear armaments.

The West consistently has refused to renounce the first-strike option because that would leave NATO forces in western Europe without a nuclear shield against the Warsaw Pact's substantially larger force of troops and conventional weapons.

Hughes pointed out that NATO leaders pledged at Bonn last summer that none of the alliance's weapons would ever be used except in response to aggression.

According to the U.S. officials, the latest proposal from the communist bloc appears to be another propaganda move aimed at giving the new Soviet leader, Yuri V. Andropov, the image of a peacemaker and fueling opposition in western Europe to scheduled deployment there of new U.S. medium-range nuclear missiles.

The U.S. strategy for countering these moves, the officials said, will be to reassert in a conciliatory manner Washington's desire for negotiations leading to a genuine easing of East-West tensions and to emphasize anew the U.S. position that the best road lies in the arms-control proposals advanced by Reagan.

Hughes underscored that point, saying, "The proposals we have made in the Geneva and Vienna negotiations on both nuclear and conventional forces are designed to achieve genuine, substantial cuts in the arsenals of both sides, as well as measures to enhance mutual confidence."

The Americans and the Soviets are conducting separate but parallel talks in Geneva on reducing both intercontinental and medium-range nuclear missiles. Talks between NATO and the Warsaw Pact on reducing conventional forces in Europe have been been going on in Vienna for almost a decade.