In informal contact earlier this year, North Korea reiterated its position that abductions of Japanese citizens in the 1970s and 1980s had been resolved, sources close to bilateral relations said Saturday.

Japan is eager to make progress in the decades-long abduction issue, possibly through a summit like that between North and South Korea on April 27, or the proposed first-ever summit between leaders of the United States and North Korea before the end of May.

But Tokyo appears to be left behind in the recent flurry of diplomatic activity and easing of tension on the Korean Peninsula, with no meeting in sight between Prime Minister Shinzo Abe and North Korean leader Kim Jong Un.

Japan informed North Korea of its desire to hold a bilateral summit through several channels since February, as Tokyo views such a meeting as essential to resolve the abduction issue.

According to the sources, Pyongyang's message about the abduction issue being settled was conveyed to Tokyo around March through an unofficial route, and not via the Japanese Embassy in Beijing as in past contact between the Japanese and North Korean governments, as Japan currently has no direct diplomatic relations with North Korea.

The Japanese government views that message as a possible attempt by Pyongyang to test Tokyo's position of insisting on the abduction issue's resolution as a precondition for improved relations, the sources said.

Abe, however, has responded by telling senior officials of the ruling Liberal Democratic Party and others that Japan does not need to feel pressured to arrange a summit with Kim, the sources said.

In 2002, five of the 17 Japanese nationals officially listed by Tokyo as abductees returned to Japan after then Prime Minister Junichiro Koizumi made a visit to Pyongyang. Japan suspects North Korea's involvement in many more disappearances.

(File photo shows five abduction victims returning to Japan from North Korea at Tokyo's Haneda airport on Oct. 15, 2002)

In July 2014, Pyongyang set up a panel to reopen an investigation in the abduction of Japanese nationals by North Korean agents, in exchange for Japan easing sanctions on the country.

But Japan reimposed the sanctions after a series of nuclear and ballistic missile tests by North Korea, which resulted in Pyongyang disbanding the investigation panel in February 2016.

Since then, North Korea has said the abduction issue was resolved.