The Reagan administration issued cautious forecasts yesterday for the outcome of next week's visit of Soviet Foreign Minister Eduard Shevardnadze but declared that the United States stands ready to expedite a Euromissiles arms agreement, the key to a next U.S.-Soviet summit.

Secretary of State George P. Shultz and chief U.S. arms negotiator Max M. Kampelman accused the Soviet Union of raising new obstacles in the nearly complete negotiations for an Intermediate Nuclear Forces (INF) treaty that would eliminate medium-range and shorter-range missiles from Europe and elsewhere.

"The Soviets keep adding new things . . . and the question is whether or not they want to move forward," Shultz said in an interview with Reuter. " . . . An agreement along the lines that have been worked out would be constructive, and we're prepared to sign it. But if they want to walk away from all of this effort, that's up to them."

Kampelman, in a news conference, said Soviet negotiators had displayed "a slowing down" of progress toward completion of a treaty in the past few weeks, leaving a number of issues outstanding that the United States had expected would be resolved by now. He also complained of "some new demands" by the Soviets.

Official sources said Shultz and Kampelman were referring to Soviet demands about U.S. nuclear warheads for West German Pershing 1A missiles stationed in Germany under a longstanding U.S.-German cooperative agreement.

In the U.S. view, the issue was resolved by West German Chancellor Helmut Kohl's Aug. 26 offer to scrap the missiles when the prospective U.S.-Soviet treaty takes full effect. But various Soviet statements, including some by arms adviser Viktor Karpov, have continued to seek more explicit promises or broader actions on this issue, which is sensitive in Washington, Bonn and other European capitals.

White House spokesman Marlin Fitzwater, at a news conference shortly after Shultz's interview and shortly before Kampelman's appearance, said the administration does not believe the Soviets are backing away from an agreement. "Our sense of it is that it's on track, that they are interested in an INF agreement and that progress is being made," Fitzwater said.

Later he said he did not believe his remarks were inconsistent with those of Shultz and Kampelman. "In the larger perspective, we still think they want an agreement, but that is not to deny there are problems," Fitzwater said.

It has been widely anticipated that if the meetings here with Shevardnadze next Tuesday to Thursday dispose of most remaining INF treaty issues, the talk will turn to a visit here late this year by Soviet leader Mikhail Gorbachev to sign the document.

Fitzwater said that "we have not received any assurances that this {Shevardnadze} meeting will produce a summit announcement." Another White House official said earlier that if the Soviets are prepared to say that "the conditions are met" for a summit meeting in Washington, the U.S. side is prepared to "get practical about dates."

The official, who asked not to be named, said it seems likely that a summit meeting here, if it takes place this fall, would be "sometime after the first week of November."

Assistant Secretary of State Rozanne L. Ridgway, however, said at a news conference that she is not aware of a single exchange between the two nations since spring about a summit and that "it's simply not part of our planning" to raise the issue with Shevardnadze.

Shultz, in two meetings with callers, promised to take up the plight of Soviet Jews and other human rights issues with Shevardnadze.

Natan (formerly Anatoly) Shcharansky, a celebrated activist who left the Soviet Union in February 1986 after nine years in prison, said his call produced agreement from Shultz that the Soviets must do more to satisfy world expectations than simply letting a few "celebrities" leave.

In a separate meeting with leaders of the National Conference on Soviet Jewry, Shultz was presented with a report saying that Gorbachev's glasnost or openness policy is at a crossroads, with several positive human rights elements contradicted by a failure to allow many previously refused applicants and prisoners of conscience to emigrate. Shultz was asked to press the issue with Shevardnadze.

Staff writer David Remnick contributed to this report.