Although the Soviet Union's position "isn't clear," the United States has "the impression and the hope" that Moscow will be ready to seek a speedy agreement on reducing medium-range nuclear missiles in Europe when the Geneva arms-control talks resume next month, a senior U.S. official said today.

H. Allen Holmes, director of the State Department's office of politico-military affairs, gave that assessment after a meeting of the North Atlantic Treaty Organization's Special Consultative Group, composed of senior diplomats representing alliance members.

The session, which preceded the winter meeting of NATO foreign ministers that starts here Thursday, endorsed the new proposal made by the United States in Geneva on Nov. 1 for reduction of intermediate-range nuclear forces (INF).

That is one of three categories, along with intercontinental nuclear missiles and space-based weaponry, under discussion in Geneva. An agreement on INF weapons, Soviet SS20 missiles in Eastern Europe and U.S. Pershing II and cruise missiles being deployed in Western Europe, is of particular interest to the NATO allies.

The Soviets have linked the three categories and insisted particularly that U.S. research in space weaponry must be stopped before progress is possible in the other areas.

Holmes, reiterating the U.S. view that "any one of the three should not be held hostage to the others," said last month's summit between President Reagan and Soviet leader Mikhail Gorbachev produced hints that the Soviets might be more flexible about moving ahead on medium-range weapons.

He declined to be more specific and stressed that a clearer answer will not be available until the Geneva talks resume Jan. 16.

The new U.S. proposal seeks agreement on an equal global ceiling for U.S. and Soviet missile warheads and would limit the United States to 140 missile launchers in Europe. The Soviets would be required to reduce by the same proportion SS20s within range of European NATO nations and other SS20s in Asia.

The Pershing II is a single-warhead missile, and the ground-launched cruises consist of a launcher unit containing four missiles. By the end of this month, Holmes said, the United States will have 140 launchers deployed in West Europe, but he refused to say how many would be Pershings and how many cruise missiles.

He said NATO counts the Soviet medium-range force at 441 launchers with 1,323 nuclear warheads. Holmes also said that, despite a moratorium on new missile deployments announced by the Soviet Union in April, NATO has detected continued Soviet construction of missile sites.