Vice President Bush, emerging tonight from a meeting with the new Soviet leader, Mikhail Gorbachev, told reporters that the time was ripe for progress in U.S.-Soviet relations.

"If ever there was a time that we can move forwards with progress in the last few years, then I would say this is a good time for that," Bush said at a press conference after his meeting in the Kremlin, which lasted an hour and 25 minutes and was attended by Secretary of State George P. Shultz and Soviet Foreign Minister Andrei Gromyko.

Bush confirmed that he had brought a letter to Gorbachev from President Reagan, and while declining to discuss the contents, he said that "the president does think a meeting will be useful."

Administration sources said in Washington yesterday that in the "personal message," Reagan invited Gorbachev to a summit meeting at a "mutually convenient time."

Reagan "would be ready when the Soviet leadership is," Bush said tonight. He did not say what Gorbachev's response was to the proposal for a summit meeting, but said he came away with "a very comfortable feeling . . . that it would be fruitful and good."

Bush's meeting with Gorbachev was delayed by more than an hour as the new Soviet leader met a stream of other visiting foreign dignitaries during his second day in office. More meetings, including those with Japanese Prime Minister Yasuhiro Nakasone and West German Chancellor Helmut Kohl are scheduled for Thursday.

Gorbachev, in his first encounters with foreign leaders as the new general secrtary of the Soviet Communist Party, was described today by the various heads of state as firm, frank and self-assured.

French President Francois Mitterrand described the new Soviet leader as "a calm man who appears willing to take on problems firmly."

"It would be a mistake to say that the advent of new leader could bring about profound changes in the politics of the Soviet Union," Mitterrand observed, however, after their 45-minute session.

Tass said Gorbachev accepted Mitterrand's invitation to visit France, but no date had been set.

British Prime Minister Margaret Thatcher, who said last December during Gorbachev's visit to Britain that she liked him and could "do business" with him, told reporters that her 55-minute meeting with the new leader today had not changed her mind.

Thatcher said their talks had concentrated on the Reagan administration's Strategic Defense Initiative, the space-based antimissile proposal also known as Star Wars. She said she told him that the 1972 antiballistic-missile treaty permitted research on such a system but that deployment would be a subject for negotiations. She said she repeated Reagan's assurance to her that this would be done.

Bush, at a briefing for western reporters at the American ambassador's residence, described his exchange with Gorbachev as "useful" and "constructive."

He said he and Shultz came away "high on hope, high that we can make progress in Geneva, high for an overall reduction of tension. Nothing happened tonight that would discourage us from that."

"We are not euphoric, not suggesting that there are not major problems, but the climate is such that we feel this is a good time to move forward," Bush said.

In describing Gorbachev's meeting tonight with Bush and Shultz, the official Soviet news agency Tass said the new Soviet leader reiterated "the Soviet Union's readiness, provided the U.S. side also was ready, to work in practice to improve" U.S.-Soviet relations. Tass said Gorbachev also stressed that the Soviet Union would "never forsake its lawful security interests of the interest of its allies."

According to Tass, Bush "made a general statement" about the U.S. administration's wish for better relations.

Bush said tonightthat the new Soviet leader made a "strong impression" and that he conducted the meeting with "great confidence and great assurance."

Gorbachev also met today with Italian President Alessandro Pertini, Nicaraguan President Daniel Ortega, the heads of the Warsaw Pact countries and others.

The seven Warsaw Pact leaders agreed to hold a summit conference in early April in Sofia, the Bulgarian capital, Eastern European sources said, according to Agence France-Presse. A summit meeting that had been scheduled to be held in Sofia two months ago was postponed because of Chernenko's illness.

Gorbachev and Ortega "vigorously condemned the U.S. policy of interference in Latin American affairs that is creating a dangerous focus of tension," Tass reported. It said the two agreed on "the necessity of a new effort to sharpen international efforts, including those of the Contadora group, for a just political settlement in Latin America." Colombia, Costa Rica, Venezuela and Mexico make up the Contadora group, which is working to ease Central American tensions.

Indian Prime Minister Rajiv Gandhi met with Gorbachev, Tass said, and the two "expressed the reciprocal desire to constantly reinforce bilateral relations on the basis of the treaties of peace, friendship and cooperation" between the two countries.

Cuban President Fidel Castro did not attend today's funeral, a sign seen by some observers as evidence of strain in Soviet-Cuban relations. Castro's brother Raul attended in his place.

During his visit here, Bush met with President Zia ul-Haq of Pakistan, Gandhi, Kohl, Nakasone and Thatcher.

The vice president has attended the funerals of two other Soviet leaders in the past 2 1/2 years and each time has met with their successors. His visit today with Gorbachev lasted longer than his 1982 meeting with Yuri Andropov and his 1984 talk with Chernenko.

Bush, who interrupted a world tour to attend Chernenko's funeral, now goes to Grenada, Brazil and Honduras. He came here after stops in central Africa.