SEOUL, South Korea (AP) — Top U.S., South Korean and Japanese officials have discussed how to achieve a complete denuclearization of the Korean Peninsula ahead of upcoming inter-Korean and U.S.-North Korean summit talks.

Seoul has said previously that North Korean leader Kim Jong Un agreed to hold summit talks with South Korean President Moon Jae-in in late April. Seoul says Kim proposed meeting with President Donald Trump, and Trump agreed to him by the end of May.

The developments have raised hopes for a potential breakthrough in the North Korean nuclear crisis.

U.S. National Security Adviser H.R. McMaster met his South Korean and Japanese counterparts in San Francisco for talks over the weekend on denuclearization and the summit talks.

South Korea's presidential office says the three agreed to maintain close trilateral cooperation.