SAN FRANCISCO, JUNE 4 -- Soviet President Mikhail Gorbachev and South Korean President Roh Tae Woo agreed today to seek full diplomatic ties between their nations.

The accord would end a 42-year official silence between the Soviet Union and South Korea and could trigger changes in political and economic relations between not only those two nations but also North Korea, China and Japan.

"Efforts to normalize relations between the Republic of Korea and the Soviet Union have already started and will lead to" full diplomatic ties, Roh told reporters through an interpreter after the meeting.

Gorbachev told reporters as he entered a car afterward that he decided to meet with Roh because of their nations' commercial ties, Reuter news agency reported. Referring to the Pacific Rim area, Gorbachev said, "We must improve relations with everyone who lives there. We can't do it selectively."

The two leaders, whose countries have not officially recognized each other since Korea was sundered in 1948, conferred for about an hour on the neutral territory of a suite in San Francisco's Fairmont Hotel shortly after Gorbachev addressed area business leaders at a luncheon there.

For days, the South Koreans had ballyhooed the session, which U.S. officials helped to arrange, while the Soviets would not acknowledge it even as it was about to take place.

Roh said he hoped the closer ties between the two nations would put pressure on North Korea to ease tensions with the South.

"The road between Seoul and Pyongyang is now totally blocked," he said. "We have to choose an alternative route by way of Moscow and Beijing."

Earlier today, Roh met for an hour with Assistant Secretary of State Richard H. Solomon here. On Wednesday, he plans to meet with President Bush in Washington.

The Soviets, who have strong economic and military ties with North Korea, could act as a mediator between the two Koreas. Neither is a member of the United Nations, and the United States does not maintain diplomatic ties with North Korea.

Soviet policy has been that only a unified Korea could be granted U.N. membership. If that position changed, it would give South Korea "legitimacy, a leverage against the North," said a U.S. official traveling with Gorbachev.

The Soviets would like expanded trade with South Korea, especially for inexpensive cars and trucks, ships and machine tools, according to U.S. officials. Trade between Seoul and the Soviets accounted for $600 million last year.

In addition, Moscow wants Seoul to help it to industrialize Soviet Siberia. By embracing South Korea, a modern-day economic and ancient cultural rival of Japan, the Soviets could prod Japan to help in that effort, too.

The Gorbachev-Roh meeting could benefit Washington as well. Eased tensions between the two Koreas could result in accelerated withdrawal of U.S. troops from Korea.

The Defense Department plans to remove as many as 7,000 of 43,000 U.S. troops stationed in South Korea over the next two years.

"There is no negative as far as the U.S. is concerned," the U.S. official said.

Further, closer ties between Moscow and Seoul could push North Korea and China closer together, analysts said.

For nearly four decades, North Korean leader Kim Il Sung has sought to maintain close ties with both the Soviet Union and China in order to avoid too much dependence on either. But in the past year, Kim has begun tilting toward China. He has not met with Gorbachev since 1986.

With impending unification of East and West Germany, the Koreas would be the last nations partitioned as a legacy of East-West tensions. More than 30 years after the end of the Korean War, tensions remain high along the 39th parallel, the dividing line between the two Koreas.

Shortly before South Korea hosted the 1988 Summer Olympic Games, Roh outlined a "northern policy," with a meeting with Gorbachev as one of its goals.

North Korea boycotted the games, but the Soviet Union, China and most Soviet-bloc nations participated. Hungary soon became the first communist country to recognize the Seoul government officially. Today, all Eastern European nations but Albania and East Germany have diplomatic ties with South Korea.

Moscow and Seoul opened trade and consular offices earlier this year.

Some Korean Americans, including about two dozen who demonstrated Sunday and today outside the Fairmont Hotel, expressed concern that the talks would result in permanent division between the Koreas.

Separate U.N. membership for the North and South would serve to legitimize the partition, according to Minn Chung of San Jose, president of Young Koreans United.

"Despite Roh's government and U.S. outspoken support reunification, what they're trying to do is divide Korea permanently by making North and South two separate nations," he said.

Other Korean Americans in the San Francisco Bay Area said they were encouraged by the meeting. "This summit will bring political and economic progress, not only to the Korean peninsula but to the Pacific Rim at large and the world," said Mary Lee Ergina, president of the Korean Residents Association of San Francisco.