Washington and Moscow are secretly discussing ways to stop North Korea from developing its own nuclear arsenal, a Japanese newspaper reported Thursday.

The Nihon Keizai Shimbun, quoting Japanese government sources, said ranking diplomats and defense officials from the two superpowers have held several rounds of talks since last summer on the subject. It did not say where.Despite official denials, hard-line communist North Korea is suspected of developing nuclear weapons based on Soviet technology provided for the North's nuclear power program in the mid-1980s.

North Korea has refused to conclude a safeguards accord with the International Atomic Energy Agency to open its nuclear facilities to outside inspection. Such an accord is required under the international treaty to prevent the spread of nuclear weapons, which the North joined in 1985.

The nationally circulated economic newspaper said the U.S. and Soviet officials are discussing, among other things, possible withdrawal of U.S. nuclear weapons allegedly stockpiled in South Korea. The aim would be to win North Korea's agreement to open itself to international inspections.

Moscow could arrange a direct meeting between officials in Pyongyang, the North Korean capital, and U.S. officials to discuss the matter, the paper quoted unidentified Japanese officials as saying.

"We have no knowledge (of this)," a Foreign Ministry spokesman said. The U.S. Embassy in Tokyo also declined to comment.

The newspaper said Japanese authorities learned of the talks from visiting Soviet Communist Party officials and U.S. defense officials.

In Washington, meanwhile, South Korean Foreign Minister Lee Sang-ock said that President Bush, at a White House meeting Wednesday, "was very concerned about North Korea's failure so far" to agree to international inspection of its nuclear projects.