MOSCOW, SEPT. 24 -- A Soviet spokesman said today that the site for this fall's meeting between President Reagan and Communist Party chief Mikhail Gorbachev has not yet been settled, putting in question assumptions that it would be in Washington.

At a press briefing, Boris Pyadyshev of the Foreign Ministry noted that a joint communique on the summit released last week in Washington did not specify where the meeting would be held. "This issue has to be addressed and has to be solved," he said.

One Soviet official, who asked not to be named, said later that the Kremlin is still reviewing the U.S. invitation to hold the summit in Washington, which he said is now a "50-50" possibility. He said an alternative site might be Hawaii, within the United States and halfway between the American and Soviet continents, but stressed that this was still speculative.

"Your side has been saying Washington, our side has been ambiguous," the official noted. He said one consideration weighing against Washington was security, and another was whether an agreement on medium- and shorter-range weapons, without a "framework" agreement on strategic cuts, warranted a state visit to the U.S. capital.

At the first Reagan-Gorbachev meeting, in Geneva in 1985, both sides announced an agreement for two more meetings -- one in United States in 1986 and one in the Soviet Union in 1987. The schedule was thrown off by the unplanned summit in Iceland last October.

A U.S. diplomat said there is still "every expectation" that the meeting would be in Washington.

A Soviet analyst said dates and a site for the summit probably would not be decided until an agreement on intermediate nuclear forces is drafted in Geneva and approved by the two sides. Moscow has said it hopes that this will be done by the time Secretary of State George P. Shultz arrives here in late October. Tentative schedules have set the summit in late November.

A framework agreement, which the Soviets have described as achievable before the end of this year, would spell out a "strict observance" of the Anti-Ballistic Missile treaty for 10 years and a pledge for deep cuts in long-range nuclear arsenals.

Washington and Moscow have expressed a willingness to intensify negotiations on strategic arms following the conclusion of the intermediate-forces accord.

The Soviet official speaking today said security considerations are a top priority in summit planning. "Gorbachev is the focus of a new policy that is too important for this country to risk him for such reasons as Soviet-American relations," he said.

At the press briefing, Pyadyshev issued a statement attacking rumors circulating about Gorbachev's health, which he said came from scandal-mongers who bear "ill will to the Soviet state."

Pyadyshev said the 56-year-old leader, who has been out of public view since Aug. 7, is on vacation in the south and will "soon return to Moscow."