The United States will continue pressing for deployment of U.S. medium-range nuclear missiles in Western Europe while at the same time seeking a joint allied position for negotiating curbs on tactical nuclear arms in Central Europe with the Soviet Union, U.S. officials said yesterday.

This two-pronged approach will be discussed with key NATO allies later this week when a U.S. team led by David Aaron, deputy national security adviser to President Carter, departs for consultations with top officials in West Germany, Britain, Italy, Belgium and the Netherlands.

The consultations were scheduled before Soviet President Leonid Brezhney offered to reduce Soviet troops, tanks and missiles in Eastern Europe in NATO abandoned plans to augment its tactical nuclear weapons in Western Europe.

But the two-pronged U.S. approach was designed to counter Moscow's diplomatic efforts to divide the Western alliance and block the planned deployment of 575 Pershing II missiles and Tomahawk Cruise missiles, each carrying one warhead, in Western Europe in the 1980s.

The Soviets this week reinforced their diplomatic drive with a personal letter from Brezhnev to NATO heads of state, including President Carter. The letter elaborated on the Soviet leader's Oct. 6 pledge to withdraw 20,000 troops and 1,000 tanks from East Germany and his offer to reduce the Eastern Europe.

The U.S. approach to the forthcoming NATO consultations is deliberately low key, combining a desire for arms reduction with an insistence on modernization of NATO's nuclear force in Europe. Adminstration officials here sought to play down the Soviet proposals and their impact on some segments of West European public opinion.

Aaron's trip to Europe this week was described as a part of routine exchanges of views between NATO officials about both arms control and NATO modernization. He will be accompanied by Reginald Bartholomew, head of the State Department's Bureau of Politico-Military Affairs, and David McGifford, assistant secretary of defense for security affairs.

But administration officials appeared concerned about West European reaction to Brezhnev's East Berlin speech, recalling an earlier Soviet diplomatic drive that blocked the deployment of a neutron weapon.

In this view, the conciliatory Soviet gestures are offset by a substantial upgrading of the quality of Soviet tactical striking forces. Defense Department officials said that while the number of Soviet missiles aimed at Western Europe remains relatively constant, the newly deployed Soviet SS20 carries three warheads instead of only one atop older rockets.

Moreover, while the SS20's range is only marginally greater, it's accuracy is estimated at three to six times greater than that of the older missiles.

U.S. officials, while expressing determination to push for NATO approval of new U.S. missiles at the NATO Council meeting in December, indicated that the number of such weapons targeted on the Soviet Union from NATO bases would depend on the Kremlin's willingness to curb its missile systems aimed at Western Europe.

Without a NATO commitment to deploy the Pershing II and TOMAHAWK, these officials say, the Soviets would on their SS20s.

Aaron's mission this week appears designed to gain allied support for this point of view while deflecting criticism the prospect of negotiated curbs on tactical nuclear arms in Central Europe.

Thus, the target figure of 572 U.S. medium-range nuclear missiles is not final and could be reduced if Moscow shows willingness to enter new negotiations.