After waiting 10 months to respond, West Germany formally has expressed its reluctance to underwrite major costs of a U.S.-proposed long-term program for modernizing and repositioning U.S. military facilities here.

The government of Chancellor Helmut Schmidt is said by both U.S. and West German sources to have left the door open for future discussions. However, conversations with these sources indicated that both budgetary and domestic political considerations will inhibit Bonn in the near term from meeting U.S. wishes.

Bonn's position was spelled out in a recent confidential reply to an eight-point U.S. program. The program outlines a variety of improvements in living conditions for the 250,000 American soldiers in West Germany and proposes a shift in location closer to the eastern front for at least some of the U.S. Army combat brigades in West Germany.

Originally envisaged to take about 30 years to complete, the U.S. plans are a comprehensive attempt to do something about the poor condition of U.S. military facilities here while bettering the strategic position of U.S. conventional forces in Europe and boosting troop morale.

Difficulty in reaching agreement on these points could become a source of renewed friction in U.S.-West German relations. The subject is on the agenda for U.S. Secretary of State Alexander M. Haig Jr. when he visits Bonn for high-level discussions this weekend.

A West German Defense Ministry source said Bonn would fulfill an earlier pledge to meet one part of the plan: a request for more wartime host-nation support. This commits West Germany to build depots, furnish supplies and assign West German Army units sometime in the next several years to service the six U.S. divisions that would be airlifted to Europe as reinforcements in a military emergency here.

But beyond that, the Defense Ministry source, citing Bonn's current austerity drive, indicated that it would not be possible for West Germany to move ahead at the moment with other projects that were requested by the United States.

A U.S. Defense Department official who is familiar with the formal West German response characterized it as neither a "flat no nor an enthusiastic yes." He said Bonn's reply is still being studied, indicating some confusion about what the West Germans were trying to say.

It seems that, after making clear the problems posed in meeting the U.S. requests, the Bonn government was simply too polite, or too politic, to say no.

No final price tag for the U.S. program is available, but the costs involved are said to be substantial.

The total program was presented to Bonn last November as an opening bid in what U.S. officials had hoped could be the start of new U.S.-West German negotiations on sharing the future cost of maintaining American forces in West Germany.

Recent West German military cost overruns and higher German payments resulting from a stronger U.S. dollar forced a cutback this year in some Bonn defense programs. Moreover, the Defense Ministry's funding request for 1982 was cut by more than half during recent budget negotiations.

Consequently, West Germany is expected to show no increase in defense spending next year after accounting for inflation.

Aside from budgetary constraints, officials here privately voice resistance to the U.S. request for peacetime support out of fear that it could set a precedent for claims by the other Western allies -- such as France, the Netherlands, Belgium, Britain or Canada -- that have troops stationed in West Germany.

U.S. officials have stressed the political realities in their talks with the West Germans. Mention has been made especially of strong sentiment in the U.S. Congress that West Europeans do more for their own defense in view of America's increased military commitments outside Europe.

A key feature of the U.S. proposal is a plan to shift at least three of 13 American combat brigades eastward, away from western and southern West Germany and closer to where West Germany borders on Warsaw Pact states East Germany and Czechoslovakia.

While the distances saved would not be great -- perhaps 100 miles or so -- such a move has been favored for years by NATO planners for the strategic gains it would still provide.

The U.S. rationale for pressing the plan now is that since the old U.S. military facilities here badly need repair, why not rebuild them in the best strategic location. By U.S. calculations, the cost of the shifts could be covered partially by the subsequent sale of currently occupied urban real estate and facilities.

Bonn officials still worry about the costs involved and, of greater concern to them, point to the domestic political problems that would be brought by environmental groups and others if U.S. troops started switching locations.

Originally, the United States also asked for West German assistance in building new family housing for military personnel under an arrangement that would provide U.S. rental guarantees to German contractors who build the housing.

In addition, Washington requested from Bonn a financial contribution for modernizing U.S. military facilities, recalling similar payments in the early 1970s.

Rounding out the U.S. program were requests for a number of smaller initiatives, including West German subsidies for certain American military activities, relief from West German administrative taxes, maintenance services performed by German contractors and relief from some environmental constraints.

U.S. officials stress the long-term nature of the proposals and remain hopeful that some basis for negotiation will be found. But the Pentagon official voiced frustration at still not being sure which, among the three Bonn ministries studying the American requests, Washington could start negotiating with.

As one sign, however, of Bonn's reluctance to get very serious about most of the U.S. proposal, the West German government does not appear to have acted on an American request to form a joint commission to deal with the matter.

The problem of covering the cost of U.S. troops here goes back several decades. In the early 1960s, concern about the negative effect such costs were having on the U.S. balance of payments led to the first set of so-called "offset arrangements."

These first came chiefly in the form of West German procurement of American military equipment. After 1968, offset arrangements provided for a mix of military procurement and West German purchases of U.S. securities, including a pledge from Bonn that dollar reserves would not be converted into gold.