Duterte had has his fourth bilateral talks with Japanese Prime Minister Shinzo Abe on the sidelines of the 31st Association of Southeast Asian Nations in Manila.
"But I can assure you that in the matter of the interest of your country and mine, we are supporting you against what North Korea is doing", Duterte said.
He hinted at the announcement while he was at the ASEAN summit in Manila on Monday where he encountered controversial Philippine president Rodrigo Duterte several times.
The leaders are also expected to unite in condemning North Korea's nuclear and ballistic missile tests. "And he should realize that he'd be responsible for ending life in this planet if his mind goes out of control", he added.
"That is why we are persuading him, maybe pleading him to stop the aggressive posture because we are not..."
"While of course, we can not deny the existence of some sensitive factors.I think both sides must work hard together to make the momentum of improvement in China-Japan relations into something solid", Li told Abe at the outset of the talks, open to the press. "The Philippines is about too far but, you know, nobody will save us from a holocaust if it happens", he added.
During the bilateral meeting which took place after the ASEAN-Japan Summit, Abe stressed that the nuclear and missile issues in the Korean peninsula were "grave and imminent" trades.
North Korea's rapidly-progressing missile and nuclear tests have heightened tensions within its neighboring regions and raised alarm in the global community.
Trump's first official visit to the region was billed as a push to step up global pressure on North Korea over its nuclear weapons program and reduce United States trade deficits with South Korea, Japan and China.
"At the end of the meeting, President Xi said this is a meeting that marks a fresh start of relations between Japan and China".