The White House and Kremlin exchanged accusations yesterday, blaming each other for blocking progress in the latest round of nuclear arms talks in Geneva.

The second round of talks on strategic and intermediate-range nuclear missiles and weapons in space adjourned yesterday for a two-month summer recess without signs of tangible progress. The talks are scheduled to resume in mid-September, two months before President Reagan and Soviet leader Mikhail Gorbachev are to hold a summit meeting in Geneva.

White House spokesman Larry Speakes said yesterday that U.S. negotiators had demonstrated flexibility in their discussion of offensive nuclear weapons and had been prepared for "detailed exchanges" on space weapons.

" . . . Regrettably, the Soviet position has remained entrenched with no movement in their formal positions," Speakes said.

But a different view was presented in Moscow where Viktor Karpov, the chief Soviet delegate in Geneva, blamed the United States for the failure of the talks.

Karpov said that nothing has changed in the arms talks since June 26, when Gorbachev accused the United States of "marking time" in Geneva, Celestine Bohlen of The Washington Post Foreign Service reported.

In that June speech, Gorbachev warned that the Soviet Union would "reassess the entire situation in Geneva" if the U.S. position remained unchanged.

"The meetings with the U.S. side that followed [the Gorbachev speech] confirmed the correctness of that assessment," Karpov said. "There was no breakthrough at the talks and the U.S. is to blame for that."

Both the U.S. and the Soviet statements on the talks dealt largely with generalities and were worded in relatively mild terms. But the major concerns of each side were evident in the comments of the U.S. and Soviet spokesmen.

The major U.S. concern is the Soviet advantage in land-based missiles, which Speakes called "the most worrisome element in the current strategic equation."

The Soviets have focused on Reagan's proposal for a Strategic Defense Initiative, called "Star Wars," which is intended to intercept and destroy offensive missiles. Karpov said that a complete ban on space weapons could open the way for "deep cuts in strategic arms -- by 25 percent or more."

The major U.S. complaint, voiced yesterday by Speakes and his deputy, Edward Djerejian, was that the Soviets have explored "concepts" for reducing offensive weapons but have refused "to deal in concrete terms and with hard numbers." Speakes said that U.S. negotiators had been prepared to discuss "specific alternative paths" leading to reductions of intercontinental ballistic missiles and medium-range missiles.

Speakes said yesterday that "we are about where we had expected to be, given that we are ending the second round of negotiations of such complexity and importance. We hope that the Soviet Union will be more forthcoming during the next round of negotiations."

Privately, U.S. officials expect little from the next round of talks. A senior official said that he considers it "unlikely" that the Soviets will want to deal in specifics or move off established negotiating positions before the Reagan-Gorbachev meeting.

"We're optimistic in the long run but progress is not going to come easily in these discussions," the official said.

This mild optimism was reflected in Geneva where Max M. Kampelman, chief of the U.S. delegation, issued a statement saying there was "a greater emphasis on dialogue and a lesser emphasis on polemics" than in the first round.

The Soviet news agency Tass took a bleaker view, saying that the United States had displayed a "patently negative nature" in the second round of talks.

In a separate disarmament forum, the United States defended research on the Star Wars program. Ambassador Donald Lowitz, chief U.S. delegate to the 40-nation Geneva Disarmament Conference, said that space weapons research does not violate the 1972 ABM treaty, as the Soviets contend.

While there have been occasional reports in both Washington and Geneva that the United States was prepared to back down on SDI in return for Soviet concessions on offensive weapons, Speakes said yesterday that the Reagan administration's position remained unchanged.

The statement that Speakes read yesterday was not seen by the president, who is recovering from surgery at Bethesda Naval Hospital. But Speakes said that its contents had been summarized for Reagan by his chief of staff, Donald T. Regan.

Speakes also announced that a 10-person White House special mission will depart for Geneva on Thursday to develop logistical recommendations for the summit meeting. The mission is scheduled to return to Washington on Monday.

A senior official said that work on a suggested agenda for the summit is in "a highly preliminary stage" and has not involved the president. Reagan is not expected to review summit issues for several weeks, although he will receive a detailed report on the results of the second round of arms talks, officials said.

Speakes said that Gorbachev had sent a "sympathetic" message to Reagan expressing best wishes for a speedy recovery