Japan has confirmed North Korea has not abandoned a 2014 bilateral agreement that led to a reinvestigation into the whereabouts of Japanese nationals abducted by Pyongyang, sources involved with bilateral relations have said.

The confirmation was made after the historic inter-Korean summit in late April, apparently during behind-the-scenes contact between Japan and North Korea, the sources said Monday.

Following the envisaged June 12 summit between U.S. President Donald Trump and North Korean leader Kim Jong Un, exchanges between Tokyo and Pyongyang over the long-standing abduction issue could also pick up pace.

But North Korea has so far maintained that the issue has been settled, and is viewed as unwilling to relaunch the investigation panel.

In 2014, Japan and North Korea agreed that Pyongyang would reinvestigate the fates of all abduction victims. But North Korea disbanded the panel and effectively abandoned the bilateral agreement in 2016.

Even though Prime Minister Shinzo Abe has prioritized resolving the abduction issue, uncertainty remains over whether the latest confirmation will lead to future progress.

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.

During behind-the-scenes exchanges between Tokyo and Pyongyang, North Korean took the view that the agreement reached in Stockholm had not been abandoned and that both sides had basically confirmed the accord was maintained, according to the sources. Japan called on North Korea to work to resolve the issue based on information collected about the whereabouts of the abductees but progress has yet to be made, the sources said.

After Trump expressed in early March his intention to meet with Kim, the Japanese government has conveyed, through multiple channels, its willingness to hold a summit between Tokyo and Pyongyang, the sources said.

Abe told a Diet session in May that any future meeting with Kim should lead to progress on the abduction issue.