SEOUL, South Korea, March 19 (AP) — Top US, South Korean and Japanese officials discussed how to achieve the complete denuclearisation of the Korean Peninsula during weekend talks ahead of upcoming inter-Korean and US-North Korean summits, Seoul said on Monday. South Korean officials who visited Pyongyang recently say North Korean leader Kim Jong Un agreed to hold talks with South Korean President Moon Jae-in in late April. Seoul says Kim proposed meeting with President Donald Trump, who agreed to meet him by the end of May. The developments have raised hopes for a potential breakthrough in the North Korean nuclear crisis. But many experts say animosities would flare again if the summits fail to produce any progress and leave the nuclear issue with few diplomatic options. North Korea has yet to confirm North Korea-US talks. US National Security Adviser H.R. McMaster met his South Korean and Japanese counterparts, Chung Eui-yong and Shotaro Yachi, in San Francisco for talks over the weekend on denuclearisation and the summit talks, South Korea's presidential office said in a statement. They agreed to maintain close trilateral co-operation in the next several weeks and shared a view that it's important not to repeat past mistakes, the statement said. It didn't elaborate but likely refers to criticism that North Korea previously used disarmament negotiations as a way to ease outside pressure and win aid while all along secretly pressing its weapons development.