U.S. and Soviet negotiators have "cleared away some significant obstacles" to completion of a treaty banning medium- and shorter-range nuclear missiles in two days of talks headed by Secretary of State George P. Shultz and Foreign Minister Eduard Shevardnadze, an administration official said yesterday.

The official, who asked not to be identified, said it is too early to say how much further progress will be made at the Shultz-Shevardnadze talks. They are scheduled to conclude at midday today.

A treaty on intermediate-range nuclear forces (INF) would be the first U.S.-Soviet arms-control treaty of the Reagan administration. Its signing is expected to be the occasion for a visit to Washington by Soviet leader Mikhail Gorbachev, perhaps this year.

As the second day of the talks began yesterday, Shultz told reporters, "We made some progress" late Tuesday in working groups on arms control. He refused to elaborate.

Shevardnadze, leaving the State Department after more than five hours of discussions with Shultz, said the talks on nuclear weapons had been "a step forward" but that "there are some points we have to work on a little more" before an INF treaty is nailed down.

The Soviet minister said, "I think we are discussing all these questions more constructively than previously." This comment was echoed by one attributed to Shultz by State Department aides that "in the past the emphasis was on problems over progress, but the emphasis now is on progress over problems."

The discussions also included Afghanistan and the Iran-Iraq war.

Soviet Foreign Ministry spokesman Gennadi Gerasimov said there is an oppportunity for important progress in the talks, especially on nuclear testing and chemical weapons. Those areas were singled out by Shultz as the talks began Tuesday as ones "where there are possibilities" for advances.

A working group on nuclear testing issues began meeting late yesterday morning. The two nations were close to an agreement at last October's Reykjavik summit on opening a special set of negotiations regarding nuclear tests. Their experts on the issue have met five times since then.

Gerasimov said the Soviets "have moved forward" on testing issues in an effort to engage the United States. "We want zero testing, but we are ready to accept four tests per year with limits of one kiloton," he said. A kiloton, the equivalent of 1,000 tons of TNT, is a very small nuclear explosion by current standards.

A U.S. official said the Soviets have spoken informally in the past about a possible one-kiloton limit for nuclear tests but said this would be unacceptable to the United States. Adherence to a limit that low could not be verified, the official said. Moreover, U.S. experts believe they need periodic tests of at least 20 to 30 kilotons in order to validate the effectiveness of weapons in the U.S. stockpile, he said.

Chemical weapons, which were discussed by Shultz, Shevardnadze and their aides yesterday, is an area "very near solution" due to recent Soviet shifts, Germasimov said.

The Soviet Union recently announced that it has stopped manufacturing chemical weapons. And last month Shevardnadze announced that Moscow would accept mandatory inspections of its chemical-weapons facilities in the context of a world-wide ban. Since then the United States has invited the Soviet Union to inspect its chemical-weapons-destruction facilities at Toelle, Utah, and the Soviet Union has invited all 40 nations in the Geneva Conference on Disarmament to send observers to a chemical-weapons-destruction facility.

There are conflicts within the Reagan administration about nuclear-testing and chemical-weapons issues, with some State Department officials more willing to accept compromises with the Soviet Union than their Defense Department counterparts.

Shultz said Tuesday, for example, that recent Soviet moves on chemical arms "are promising." But a senior Defense Department official said last week that "I can't conceive of a chemical-weapons ban that would be verifiable and in our interest," adding that it would be "irresponsible folly" to accept a global ban.

The intra-administration tension on some arms issues was suggested by the exclusion of senior Pentagon arms-control officials and special arms adviser Edward L. Rowny from a meeting with Shevardnadze's team Tuesday. Staff writer R. Jeffrey Smith contributed to this report.