LOS ANGELES, DEC. 27 -- President Reagan today called upon Soviet leader Mikhail Gorbachev to translate his "declared intentions into reality by promptly and irrevocably withdrawing all Soviet forces from Afghanistan."

In a one-page statement issued on the eighth anniversary of the Soviet invasion of Afghanistan, the president said, "Let 1988 be the year of action, the year that will see the Soviet Union end once and for all its brutal occupation of Afghanistan."

The statement was issued to reporters without comment as the president and Nancy Reagan were en route to Los Angeles for a week's vacation in California. They will spend two days here and then leave for Palm Springs, where they will be the guests of publishing magnate Walter Annenberg.

While Reagan is scheduled to review an early text of the State of the Union message he will deliver on Jan. 25, the president has made no secret that he intends to spend most of the week relaxing. Asked as he was leaving the White House about his New Year's resolutions, Reagan smiled and bounced a golf ball he was carrying.

Reagan and Gorbachev also plan an exchange of New Year's messages, as they did two years ago. White House spokesman Marlin Fitzwater said on Air Force One en route from Andrews Air Force Base that the president's message already had been videotaped and delivered to the Soviet Embassy.

"They tentatively said they'd use it if the U.S. networks use Gorbachev," adding that the networks had yet to make a commitment.

In his statement today on Afghanistan, the president said that he and Gorbachev had discussed the issue at their Washington summit earlier this month. Reagan said he had asked Gorbachev to announce both a timetable for withdrawal and a firm date it would begin.

Gorbachev told Reagan that the Soviets had reached a decision to withdraw from Afghanistan, according to officials of both countries. But the Soviets insist that the United States must cease military aid to the Afghan resistance. The U.S. view has been that the Soviets should withdraw without preconditions, and that aid to the rebels would then no longer be necessary.

While Gorbachev gave no timetable for withdrawal during the summit, some U.S. officials afterward expressed optimism that the Soviets would soon begin reducing their military presence in Afghanistan. Instead, they recently launched a new winter offensive.

Reagan's statement today, similar to others issued on the anniversary of the invasion, called the Soviet action of Dec. 27, 1979, "an unprovoked and blatant affront to both human decency and international law."

The president said the Soviet effort had been unsucessful, despite the killing of a million Afghans and the creation of five million refugees.

"The Afghan people will not be conquered," Reagan said. "With an abiding faith in God, and a passionate love of freedom, they have shown the world what price free people are willing to pay to remain free. They remind us that freedom is not a gift, but a cherished prize to be won and preserved by ceaseless struggle."

The president's light schedule for the week includes two events on Jan. 2 -- the signing of the U.S.-Canada free trade agreement and the opening of the $20 million Bob Hope Cultural Center in Palm Desert.

During his two days in Los Angeles, Reagan will have his annual appointments with his allergist and his ear doctor, Fitzwater said.

On New Year's Eve, the Reagans will be guests of honor at an annual black-tie party that has become a traditional reunion for other dignitaries and some of their closest friends.