Japan has sounded out North Korea about its plan to establish a liaison office in Pyongyang to resolve the long-standing issue of past abductions of Japanese nationals by the North, sources familiar with bilateral relations said Sunday.

Tokyo hopes to get to the bottom of the issue and secure the repatriation of the abductees with the plan that was conveyed to the North Korean side through informal contacts, according to the sources.

But the outlook for a major breakthrough on the abduction issue remains uncertain as North Korea's response has reportedly been blunt.

(Undated supplied photo shows Megumi Yokota before being abducted by North Korea in 1977 at age 13)  

Japan has also expressed its readiness to cooperate in allowing North Korean athletes to enter the country when Tokyo hosts the 2020 Olympics and Paralympics and to work toward settling the "unfortunate past" based on the Japan-North Korea Pyongyang Declaration in 2002, the sources said.

The Pyongyang declaration touched on the "tremendous damage and suffering" Japan caused to the people of Korea during its colonial rule that ran from 1910 to 1945.

The latest approach is seen as a fresh attempt by Tokyo to lay the groundwork for a Japan-North Korea summit, as North Korean leader Kim Jong Un has been stepping up diplomacy by meeting with U.S. President Donald Trump and Chinese President Xi Jinping.

For his part, Prime Minister Shinzo Abe is eager for bilateral talks with the North Korean leader, saying he wants to seize "every opportunity" for direct talks to resolve the abduction issue.

Japan officially lists 17 nationals as having been abducted by North Korean agents in the 1970s and 1980s but alleges their involvement in many more disappearances. Five of the 17 were repatriated in 2002.

The proposed opening of a liaison office is based on a bilateral agreement reached in 2014 in Stockholm that says Japanese officials will stay in North Korea to check the progress of Pyongyang's probe into the abduction issue.

Japan and North Korea agreed back then that Pyongyang would reinvestigate the fates of all abduction victims. But North Korea disbanded the panel and effectively abandoned the bilateral agreement in 2016.

North Korea has said the findings of the probe were conveyed to Japan but Tokyo has maintained that no explanations were made.

Abe has expressed willingness to settle diplomatic challenges left unresolved since the end of World War II.

His intention to meet with Kim has been relayed by Trump and South Korean President Moon Jae In. Moon, who met with Kim in September, has told Abe that the North Korean leader is ready to engage in direct talks with Japan at an appropriate time and improve relations.

Some family members of the Japanese abductees expressed anxiety.

Shigeo Iizuka, who heads a group representing the abductees' families, said Japan should first get an assurance from North Korea that all abductees will return immediately.

"If (the liaison office) is set up before that, we may not be able to see progress" on the abduction issue, Iizuka said.