The Reagan administration is approaching the climax of a year-long skirmish with critics who want it to punish Soviet abuses of human rights by imposing stiff restrictions on Soviet imports produced with "slave labor."

The dispute turns on whether to ban up to half of the Soviet goods and material entering the United States by extending a rarely applied 1930 ban on imports believed to be made with forced labor.

Secretary of State George P. Shultz and other members of the Cabinet are reported to have warned that use of the import restriction could produce a trade war that could be far more damaging to lucrative U.S. grain sales to the Soviet Union than it would be to the Kremlin.

Members of Congress and other advocates of the ban question whether it would bring on a trade war. In any event, they maintain, the administration has no choice under existing law but to enforce it.

If a broad ban had existed in 1982, it is estimated that it could have barred $138 million of the $227.5 million in imports from the Soviet Union. U.S. exports to the Soviet Union that year were lopsidedly greater: $2.6 billion, of which $1.85 billion was in grain sales.

This is a sensitive dispute for an administration that stresses its readiness to negotiate on all sources of superpower tension but that has been vocal in denouncing Soviet practices. Administration attacks on "slave labor" helped to arouse the demand for the trade restrictions.

U.S. Customs Commissioner William von Raab informed Treasury Secretary Donald T. Regan in September 1983 of his plan to begin applying the forced-labor ban against 36 Soviet products. Regan is reported to have supported the plan until it ran into tough opposition from Shultz, Commerce Secretary Malcolm Baldrige, Agriculture Secretary John R. Block, and U.S. Trade Representative William E. Brock.

Regan decided last May to postpone a ruling on the ban until after Nov. 12, when the International Trade Commission is scheduled to complete a fact-finding study requested by Sen. Robert J. Dole (R-Kan.), chairman of the Senate Finance Committee.

That timetable pushed the dispute beyond the election campaign, in which President Reagan has used Soviet grain sales to court the farm vote. Reagan on Sept. 11 announced U.S. readiness to sell an additional 10 million tons of wheat and corn to the Soviet Union.

Dole is a champion of Soviet grain sales, as are many members of Congress, but he was among 45 senators who urged the administration last October to enforce the ban against the Soviet Union. In May, 84 House members made a similar appeal.

Last month a lawsuit to force the administration to enforce the ban was filed on behalf of several groups, including 33 Republican and Democratic members of the House and two perennial critics of the administration's Soviet policy, Sens. Jesse Helms (R-N.C.) and Steven D. Symms (R-Idaho).

The Sept. 26 complaint in the U.S. Court of International Trade in New York charged the administration with "abitrary, capricious" and illegal action, and "an abuse of discretion" in failing to apply the law. Named as defendants were von Raab and Assistant Treasury Secretary John M. Walker Jr. The suit was filed by Daniel J. Popeo and Paul D. Kamenar of the Washington Legal Foundation.

At issue is a section of the 1930 Smoot-Hawley Tariff Act, which bars imports of articles or material made in whole or in part with "convict labor" or "forced labor." In the past it has been used primarily to protect U.S. companies from underpriced foreign products made with cheap prison labor, and was invoked against only one Soviet product, crabmeat, from 1950 to 1961, at the height of the Cold War.

Current requirements for blocking imports are so broadly written that the customs commissioner can order the seizure of suspected goods if he has "information that reasonably but not conclusively indicates" that they are subject to the ban. It is up to the shipper or importer to prove that the imports were not made with forced labor.

During the past year, however, the Reagan administration has moved away from that sweeping criteria. Critics charge that the administration is deliberately watering down its impact on the Soviet Union. Administration officials counter that the ban has been applied inconsistently and must be uniform for all nations.

Regan said on May 17 that after the International Trade Commission study on Nov. 12, standards for applying the ban should include "a specific finding that the use of forced labor gives that foreign producer a more than de minimus small price advantage over American producers." In addition, Regan said, the customs commissioner should consider such factors as "the apparent value added by use of forced labor," the "percentage of time" contributed by such labor and "whether labor cost is a significant component."

As administration concern about applying the ban has increased, it has increasingly questioned the adequacy of its intelligence data for enforcing it.

Initially, in February 1983, responding to a resolution sponsored by Sen. William L. Armstrong (R-Colo.), the State Department said the Soviet Union operates the world's largest "forced labor system" that "gravely infringes internationally recognized fundamental human rights," with an estimated 4 million workers in 1,100 camps. Of that number, the report said, "at least 10,000 are considered to be political and religious prisoners."

At that stage, using CIA information, advocates of the ban envisioned applying it to a long list of Soviet imports, from petroleum and chemicals to gold, uranium, wood products, glassware, machinery parts, aluminum and tea.

By the following November, however, in a joint hearing by the House Committee on Foreign Affairs and the Commission on European Security, administration witnesses stressed the lack of "specific evidence" about forced labor in particular products, the need for applying uniform criteria "to all countries" and "the potential economic problems that enforcement could produce for United States business."

Rep. Dante B. Fascell (D-Fla.) is chairman of that committee and co-chairman, with Dole, of the commission, which has been especially active in seeking action on the forced labor issue.

In the hearing, Walker said that as a result of Cabinet-level discussion, the administration had asked the CIA for "a more intensive examination of the factual basis which would support enforcement of the statute."

The report that emerged cast a cloud over the whole subject. CIA Director William J. Casey reported to Regan on May 16 that, "although there is convincing evidence that convict and forced labor is used extensively in the Soviet Union, it is fragmentary with respect to specific products."

Casey said it is not "sufficiently precise to allow us to determine whether and to what extent the products of forced labor are exported to the United States" nor could the CIA, without danger to "intelligence sources and methods," produce evidence adequate for "a legal proceeding with respect to a particular product."

As a consequence, Regan said, "we cannot, with currently available information, determine which products are produced in this manner and which are not," and "I do not believe the American people want their government to act precipitously . . . in a matter of such importance to our international relations."

Regan held out the hope that the trade commission study will clarify the dispute. The trade commission, however, is dependent on the same sources for intelligence data, and it will focus on the economic consequences of Soviet imports. Administration critics contend that the government "is stalling" and that by broadening requirements for enforcing the ban, it has set unattainable standards. Therefore, they say, they felt compelled to go to court.