MOSCOW, JULY 31 -- Soviet Foreign Minister Eduard Shevardnadze called today for a speedup in preparations for the next Soviet-U.S. summit meeting, which, he said, has been agreed upon for later this year.

Shevardnadze was speaking to Soviet journalists aboard a special plane taking him to the Siberian city of Irkutsk for talks Wednesday and Thursday with Secretary of State James A. Baker III, who flew in after meetings with Southeast Asian allies in Singapore. It was the first time that an official of either superpower had publicly raised the likelihood of a second meeting this year between presidents Gorbachev and Bush.

In Washington, a senior administration official said that no specific plans have been made for a second summit this year but that one might be possible if a strategic-arms accord is complete and ready for signing, Washington Post staff writer David Hoffman reported. "I can't see a summit in advance of closure" on a strategic-arms treaty, the official said.

There have been reports that Baker and Shevardnadze are close to agreement on a settlement in Afghanistan, where U.S.-backed rebels are engaged in a bitter civil war against the Soviet-supported government of President Najibullah. Speculation of a possible breakthrough was fanned by Najibullah's unexpected arrival in Moscow Sunday for what was officially described as "medical treatment."

The Soviet news agency Tass quoted Shevardnadze as saying Soviet and U.S. positions on Afghanistan had been "coming closer together" recently. "The issue of a settlement is now being posed differently," he said, without elaborating.

According to Tass, Shevardnadze said that agreement on a U.S.-Soviet summit later this year had been reached by the two presidents last December in Malta. The news agency said the Soviet foreign minister had explained that there was "now extremely little time left to prepare the new summit."

Bush and Gorbachev last met in Washington in early June, when they agreed on the broad principles for a new agreement limiting strategic nuclear weapons. No date was announced for their next meeting, but it was expected that Bush would travel to Moscow next year to sign such an accord.

By revealing the Malta discussion about a second summit this year, Shevardnadze appeared to be trying to elicit from the Bush administration a specific date. The Soviet leadership is anxious to demonstrate that Gorbachev's policy of detente with the West has produced tangible results during a period of deepening domestic worries over the economy and ethnic turmoil.

It was not immediately clear where a summit meeting later this year would be held. In theory, it is Bush's turn to visit the Soviet Union, but the two leaders could also meet on neutral territory. Western diplomats here speculated that a meeting could be arranged following a session of the 35-nation Conference Security and Cooperation in Europe (CSCE) that is due to be held in Paris in November. Gorbachev also has accepted in principle an invitation to visit NATO headquarters in Brussels.

Shevardnadze told the Soviet reporters that his talks with Baker also would focus on such regional problems as Afghanistan and European security. His deputy, Alexei Obukhov, said the strategic-arms limitation treaty, or START, would be a principal item on the agenda.

The meeting on the shores of Lake Baikal, which Russians regard as one of the natural wonders of the world, is designed to repay the hospitality Shevardnadze received from Baker at Jackson Hole in Wyoming last year.

A possible deal on Afghanistan would be likely to involve the cutoff of military supplies to both sides and an agreement on a timetable for free elections. It would also have to address the future role of Najibullah, whose removal from office has been demanded by the guerrillas as a precondition for talks and the formation of a provisional government.

The Soviet Union pulled its troops out of Afghanistan last year, after a 10-year presence but continued to channel aid to government troops. Najibullah's ability to survive in office for a further 16 months after the Soviet withdrawal confounded many analysts and allowed the Kremlin to claim that it had secured an honorable exit.

Shevardnadze also mentioned Cambodia as another area of discussion with Baker, saying that he hoped to map out a program for future action on the civil war there. The U.S. decision to talk to Vietnam and cut ties with the extremist Khmer Rouge guerrilla group has effectively removed much of the friction between the two superpowers over Cambodia.

Hoffman added in Washington:

After the Washington summit in June, Bush said that he and Gorbachev had agreed "to meet on a regular basis, perhaps annually." They also agreed to push negotiations on a strategic-arms treaty, but officials said it is not yet clear if it will be ready for signing by year's end.

The United States and Soviet Union also are trying to complete a separate treaty on reducing conventional forces in Europe in time for signing at the CSCE meeting in November. U.S. officials said Bush and Gorbachev are expected to attend and could hold a separate meeting there.

The U.S. officials said they were taking Shevardnadze's comments seriously as a signal of Soviet interest in another summit. If Shevardnadze proposed it to Baker, the officials said, the U.S. response would likely be that a summit could be scheduled when it looks convenient for both sides and when a strategic-arms accord is ready to be signed.

State Department officials in Washington continued to express only muted hopes for an Afghan settlement in Irkutsk, saying concessions from the Soviets would be required. Washington looked favorably on a possible compromise floated last month by Soviet U.N. Ambassador Yuli Vorontsov, in which Najibullah would hand off control of the powerful defense, security and information ministries to an internationally supervised transitional administration to ensure the government's neutrality in an election.

But State Department and other officials said that in the last two weeks Najibullah has spoken of a need to limit sharply the powers he would relinquish. Diplomats, including one with close ties to the Kabul government, said Najibullah's trip to Moscow appeared to be for discussions of any U.S.-Soviet agreement.

James Rupert of The Washington Post Foreign Service contributed to this story in Washington.