President Bush and South Korean President Roh Tae Woo publicly assured North Korea yesterday that the recent dramatic improvement in the Moscow-Seoul relationship does not presage any security threat to the heavily armed regime in Pyongyang.

"The United States reaffirms that it is not a threat to North Korean security, and we seek to improve relations with that country," White House spokesman Marlin Fitzwater told reporters following the 45-minute meeting of Bush and Roh.

A South Korean spokesman said Roh asked Soviet President Mikhail Gorbachev at their groundbreaking meeting Monday in San Francisco to pass along assurances to the North Korean regime. "We do not seek military superiority over North Korea, and we have no intention to attack North Korea," the spokesman quoted Roh as having told Gorbachev.

U.S. and South Korean officials said the unusual statements of reassurance reflected concern that the unpredictable North Koreans may feel threatened by South Korea's unprecedented top-level contact with the Soviet Union, which has been a key sponsor and ally of North Korea since the peninsula was divided in 1945. "The North Koreans are quite worried and angry after this meeting {with Gorbachev}," said an aide to Roh.

Roh also asked Gorbachev to convey to Pyongyang his desire to meet North Korean President Kim Il Sung to restart the stalled North-South peace process, the aide said. In addition, Roh told Gorbachev that North Korea should open up to the outside world, and that South Korea stands ready to assist the North in doing so, according to the Korean official.

North Korea's Central News Agency, in the first official reaction to the Roh-Gorbachev meeting, yesterday attacked what it described as "two-Korea plotters" and "splittists within and without" whose activity could "threaten world peace." The dispatch did not mention the Soviet Union by name but seemed directed in part against Moscow, Reuter reported.

Bush told reporters that the Roh-Gorbachev meeting was "very important," and reiterated his "strong support" for Roh's policy of expanding ties with the communist world, according to Fitzwater.

The White House spokesman said the "pace and scope" of any improvement of U.S. ties with North Korea will depend on North Korea's actions. Specifically, Fitzwater called on Pyongyang to complete arrangements for international inspection of its nuclear facilities, under discussion with the International Atomic Energy Agency for several years.

South Korean sources said Seoul began putting out feelers to the Kremlin in February that Roh would be interested in a meeting with Gorbachev. Several Korean business and governmental channels were used.

At one point this spring, Roh had planned a private visit to Washington in May to enlist Bush's assistance in arranging a meeting with the Soviet leader. There was even talk of a three-way Bush-Gorbachev-Roh meeting here, the sources said, though neither Washington nor Moscow seems to have taken this idea very seriously. Several weeks ago the Roh trip to Washington was cancelled.

The startling news that Gorbachev was ready to meet the South Korean president in San Francisco came from former Soviet ambassador to the United States Anatoliy Dobrynin, now an adviser to Gorbachev, who was in the South Korean capital late last month for a meeting of retired world leaders, according to an informed source.

Many reports suggested that Gorbachev agreed to see Roh, thus upgrading his relations with Seoul, primarily because of the economic potential of deals with the increasingly prosperous South Koreans.