SHANNON, Ireland (AP) _ Secretary of State James A. Baker III met with the Soviet foreign minister Tuesday and agreed to visit Moscow in May, where they will discuss prospects for a Bush-Gorbachev summit.

His two-hour meeting with Eduard A. Shevardnadze in Vienna took place the day after they outlined their governments' positions at a 35-nation conference on reducing conventional military forces in Europe. Baker's plane made a refueling stop in Shannon on the flight home.

Baker resisted a Soviet overture to reopen negotiations in April or May on reducing long-range - or strategic - nuclear missiles. He said the Bush administration wants to complete parallel reviews of its arms control policy and nuclear force structure before resuming the talks.

Reopening the talks on long-range bombers, nuclear submarines and missiles will be discussed during the visit to Moscow in the first half of May, after the parallel studies are completed in April, he said.

In Vienna after the meeting, Baker told reporters the United States ''is not ready to set a date'' at this point for a summit between President Bush and Soviet President Mikhail S. Gorbachev.

The secretary criticized the Soviets about Iran and military aid to the leftist Sandinista government of Nicaragua. He said Moscow was ''posturing'' on Iran, which Shevardnadze visited recently, and had helped arm Nicaragua in a ''way out of proportions'' manner that threatens its Central American neighbors.

A senior State Department official traveling with Baker said the Soviet offer to mediate the furor over British writer Salman Rushdie's novel ''The Satanic Verses'' interferes with a U.S. campaign to isolate Iran.

Iran's fundamentalist Shiite Moslem regime believes the novel blasphemes Islam and its patriarch, Ayatollah Ruhollah Khomeini, has ordered his followers to kill the author. Iran broke relations with Britain on Tuesday because it did not condemn the book and prosecute Rushdie.

Despite clear differences on those and other issues, the get-acquainted session between Baker and Shevardnadze appeared to go well. Baker said it was held ''in a very positive atmosphere, reflecting a determination to cooperate.''

As they parted at the residence of Henry Grunwald, the U.S. ambassador to Austria, Shevardnadze ''told me it was a very good beginning, and I would agree with that,'' Baker said.

Baker objected to the Soviet attempt in Vienna to seek reductions in combat aircraft and naval forces and also eliminate short-range, or battlefield, nuclear weapons. He said the mandate for negotiations that begin Thursday excludes missiles and ships.

Shevardnadze's proposal for separate negotiations on the nuclear weapons with ranges of up to 300 miles conflicts with U.S. determination to keep Lance missiles in West Germany and triple their current range of about 70 miles.

On Monday night, a senior State Department official briefing reporters under rules of anonymity said the Soviets were looking for ''fissures'' in the Western alliance.

Chancellor Helmut Kohl of West Germany has proposed delaying the Lance modernization for two or three years.

On the trip home, Baker said Soviet suggestions for conventional force reduction were ''remarkably close to the NATO proposal.''

NATO has called for sharp reductions in Warsaw Pact tanks, artillery and armored personnel carriers to Western levels, followed by additional cuts of 5-10 percent on both sides.

Shevardnadze proposed a first-phase reduction of 15 percent by 1992 and 40 percent by 1995.

U.S.-Soviet negotiations to reduce long-range arms have been suspended for three months. In mid-February, Bush postponed a resumption until the policy review was completed.

Shevardnadze told a news conference in Vienna he suggested to Baker the talks resume in April or May but the secretary said the United States ''will need more time.''

On the plane, Baker said he told Shevardnadze it was ''premature to lock in on a date now,'' with the review in process. He added to reporters: ''It is our strong desire to build on the progress that has been made to date.''

When the talks were suspended, negotiators had reached tentative agreement on several weapon ceilings but were having trouble on ways to guard against cheating.