MOSCOW, SEPT. 22 -- Soviet leader Mikhail Gorbachev, who has not been seen publicly since Aug. 7, is still on vacation and in excellent health, a Foreign Ministry spokesman said today.

Deputy information director Boris Pyadyshev denied rumors now circulating in Moscow that Gorbachev, 56, is recovering from an undisclosed ailment. He gave no date for the leader's return to work, saying the Kremlin does not release such information in advance. This year, for the first time, the Soviet press did not announce when the general secretary went on holiday.

The rumors of Gorbachev's illness, similar to ones that surfaced during his vacation last summer about an unconfirmed assassination attempt against him, were given wider currency by a report in the West German newspaper Bild Zeitung that Gorbachev had been stricken with food poisoning and hospitalized.

Pyadyshev stressed that in Gorbachev's absence, the Soviet government had given a positive assessment of the U.S.-Soviet accords reached in Washington last week on a pending agreement to eliminate medium-range and shorter-range nuclear missiles.

The Soviet spokesman said remaining technicalities could be resolved by U.S. and Soviet negotiators in Geneva over the next month if both sides "apply all efforts and work day and night."

He noted, however, that a final draft, while desirable, was not essential for the meetings scheduled here late next month between Secretary of State George P. Shultz and Soviet Foreign Minister Eduard Shevardnadze. Pyadyshev said 70 pages of the treaty text already had been prepared.

Pyadyshev also said no definitive date had yet been set for the Shultz visit, but that he saw no objections to Oct. 20, a date now being mentioned in Washington.

Among the differences still to be resolved are procedures for the phased reduction of nuclear weapons, Pyadyshev said. He said the United States has proposed leaving missiles operational until their elimination, while the Soviet side has proposed making them inoperative from the start of the process.

He said the Soviet Union "would be agreeable" to a U.S. proposal to destroy shorter-range missiles over one year and medium-range missiles over three years if it proves "technically and environmentally" possible.

"Otherwise, we are prepared to be most cooperative in relations with the Americans," said Pyadyshev, noting that the destruction of the weapons could prove difficult and costly.

Pyadyshev stated, however, that the Reagan administration's Strategic Defense Initiative continued to stand in the way of progress on reductions of strategic nuclear weapons. The Soviet Union has proposed a commitment by both sides to adhere to a strict interpretation of the 1972 Anti-Ballistic Missile treaty for 10 years as a way of limiting development of the U.S. "Star Wars" program.

"If this is not done, radical reductions {in strategic weapons} will be out of the question," Pyadyshev said. "There were no promising signs from indications from the U.S. side."