President Reagan is planning to respond to Soviet leader Mikhail Gorbachev's recent letter containing wide-ranging arms-control proposals with one of his own that emphasizes seeking reductions of U.S. and Soviet intermediate-range nuclear missiles in Europe, according to U.S. officials.

"The working assumption is that this is the most lucrative field," one official said yesterday. However, sources said, it may take a week to devise the administration response.

One administration concern is that Gorbachev may have linked progress in medium-range missile reductions to a concession in Reagan's Strategic Defense Initiative, the "Star Wars" research program, officials said.

In his Jan. 15 letter, Gorbachev said reduction of long-range strategic weapons "is possible only" if the United States joins the Soviets in renouncing "development, testing and deployment" of space weapons. He also tied all nuclear reductions to a ban on space weapons.

A Soviet diplomat here said yesterday that medium-range reductions could go forward without agreement on space weapons.

He added, however, that Moscow "hoped" that the administration would be willing to discuss limiting space weapons in exchange for progress in negotiating the 50 percent reduction in longer-range systems. Reagan and Gorbachev agreed to that during their November summit.

Administration officials said Reagan's response is expected to ask the Soviets to reduce sharply the number of medium-range missiles still in the Far East and to detail a plan for destroying the European-based missiles. In both cases, they said the specifics will have to be discussed at arms talks that resumed recently in Geneva.

In addition, administration officials said Reagan is expected to tell the Soviets that they must discuss with Britain and France Gorbachev's proposal that the two will have to pledge not to build up their forces as part of the medium-range missile agreement.

Longtime differences within the administration have resurfaced during interagency discussions on how to respond to Gorbachev.

Key Defense Department officials have criticized his plan as a propaganda effort rather than a serious effort to spur negotiations. State Department officials, on the other hand, have argued that Gorbachev's appeal for public support included initiatives that deserved to be followed up.

Yesterday, several officials of past administrations called on Reagan to respond to Gorbachev.

Paul Warnke, director of the Arms Control and Disarmament Agency under President Jimmy Carter, urged the administration to "get serious about arms control." He said that, if the Soviet proposal "is a bluff, let's call the bluff."

Ambassador Gerard Smith, chief negotiator of the SALT I agreement under President Richard M. Nixon, said he is "very dubious" that the administration can devise a realistic response.

In a related matter, the West German parliament was told that the first 16 U.S. ground-launched cruise missiles will be deployed in West Germany in March.

In a statement, Defense Minister Manfred Woerner said the first missiles would go to Hahn Air Base near Bonn while a permanent facility is constructed. The full wing of 96 American missiles will be completely installed by the end of next year, he said.