SEOUL—North Korea has no plans to improve ties with Japan unless Tokyo first resolves historical issues between the two countries, South Korean sources said.

North Korean officials who attended an international conference in Shenyang, China, in late August showed no interest when South Korean attendees suggested they tighten ties with Japan to elicit economic assistance, the sources said.

The North Korean officials said improving ties with Japan was not a priority, and that Tokyo should resolve historical issues first and everything else would follow, according to the sources who are familiar with the contents of the meeting.

North Korea has no diplomatic ties with Japan, which colonized the Korean Peninsula from 1910 to 1945.

The five North Korean officials at the meeting included Ri Son Ung, an official of the National Reunification Institute, which is overseen by the United Front Department of the Workers’ Party of Korea.

According to a source familiar with Tokyo-Pyongyang relations, Shigeru Kitamura, a top official at the Cabinet Intelligence and Research Office, met with Kim Song Hye, a senior North Korean official in charge of reunification, in July.

But the North Korean officials’ remarks in Shenyang indicate that no progress has been made between Tokyo and Pyongyang since the Kitamura-Kim meeting.

“North Korean officials believe that if relations between Pyongyang and Washington are enhanced, then their country’s ties with Japan will follow suit,” said a South Korean official who attended the Shenyang meeting. “But since North Korea and the United States are now in a diplomatic stalemate, they apparently see no point in meeting with Japanese officials.”