SEOUL, MAY 30 -- President Roh Tae Woo, seeking a diplomatic breakthrough for South Korea, will make an unscheduled trip to the United States to meet Soviet President Mikhail Gorbachev after the U.S.-Soviet summit.

U.S. officials said Roh will meet Gorbachev on Monday in San Francisco. Diplomatic sources in Washington said the South Korean president then may come to Washington to see President Bush.

The meeting would be a triumph for Roh's policy of opening relations with nations that traditionally have backed North Korea, one of the world's last hard-line Communist states and technically still at war with South Korea. The Soviet Union is slowly backing away from North Korea, a longtime ally, and a Roh-Gorbachev meeting likely would enrage Pyongyang, which has reacted angrily to Seoul's inroads with Moscow and Eastern Europe.

South Korea has consular but not full diplomatic ties with the Soviet Union. In the only previous contact between Gorbachev and a South Korean official, a co-leader of the ruling party briefly met the Soviet president in Moscow earlier this year.

At the meeting, Roh and Gorbachev might announce their intention to establish full diplomatic ties, sources said. South Korea also wants to reverse Moscow's longtime opposition to its entry to the United Nations, which North Korea opposes on the ground that the move would prolong the division of Korea.

Roh likely would ask for Soviet help in improving Seoul's ties with Pyongyang, the sources said. Moscow is better positioned to act as a diplomatic broker than the United States, which does not have diplomatic ties with North Korea. South Korea and the United States have been urging the Soviets to press North Korea to allow open inspection of a nuclear facility allegedly being used to develop weapons.

Most South Koreans would enthusiastically support a Roh-Gorbachev meeting, but conservatives have shown signs of unease over their nation's rapid rapprochement with the Soviet Union. The conservatives oppose major South Korean investment in the Soviet Union -- a key factor in Moscow's interest in developing ties with Seoul.

A South Korean newspaper reported in its first edition today that Roh and Gorbachev would meet in San Francisco, the last leg of Gorbachev's visit. A diplomatic source said the article was mistakenly published after an off-the-record Foreign Ministry briefing for South Korean reporters, and it did not appear in the paper's later editions.