The government has conveyed to North Korea its desire to hold a summit between Prime Minister Shinzo Abe and North Korean leader Kim Jong Un, diplomatic sources have said.

Abe wants Kim to resolve the issues of past abductions of Japanese nationals by North Korea and Pyongyang’s nuclear and missile development programs, saying that implementing the Japan-North Korea Pyongyang Declaration signed in 2002 will bring economic benefits to Pyongyang, the sources said Wednesday.

With summits expected between Kim and South Korean President Moon Jae In in April and U.S. President Donald Trump in May, Japan is concerned that the abduction issue may be left behind, they said.

Japan and North Korea have held summits twice in the past, when then-Prime Minister Junichiro Koizumi held talks with Kim’s late father Kim Jong Il in Pyongyang in 2002 and 2004.

The declaration they signed says Japan will extend economic cooperation to North Korea after normalizing relations.

At that landmark summit in 2002, Kim Jong Il admitted that North Korea had abducted 13 Japanese and said eight had died. North Korea allowed five abductees to return to Japan in October 2002, but no tangible progress has been made since then.

North Korea says the abduction issue has been resolved, while Tokyo is seeking the return of all victims.

In seeking to realize the summit with Kim, Abe will ask for Trump’s cooperation during their meeting in the United States as early as mid-April, the sources said.

But as Japan maintains the stance of adding pressure on North Korea over its nuclear and missile development programs, it is uncertain whether North Korea would be willing to hold a summit with Abe. Abe has also repeatedly said that dialogue with North Korea for dialogue’s sake is meaningless.

On Feb. 9 in Pyeongchang, South Korea, Abe told the North’s nominal head of state, Kim Yong Nam, that there is no change in Japan’s stance of seeking normalization of diplomatic ties by resolving the abduction, nuclear and missile development issues based on the Pyongyang Declaration, according to a source close to the matter.

In the meeting, Kim Yong Nam did not deny the necessity of normalizing ties, the source said.

“(Abe’s) reference to normalization signals his enthusiasm for top-level talks. The North Korean side also took it that way and his intention has been conveyed” to Kim Jong Un, the source said.

Earlier this month, Foreign Minister Taro Kono separately asked U.S. Vice President Mike Pence and South Korean Foreign Minister Kang Kyung-wha to convey to North Korea Japan’s desire to hold talks with Kim, a diplomatic source said.

In February, Mongolian Foreign Minister Damdin Tsogtbaatar also told the North Korean side about Japan’s stance regarding a summit with Kim, which received a positive response, according to the source. Mongolia traditionally maintains friendly ties with Pyongyang.