Mattis said the regional powers need to implement all UN Security Council sanctions on Pyongyang in place.

"North Korea will receive relief only when it demonstrates verifiable and irreversible steps to denuclarization."

The South's minister also said he was "quite cautious," given the North's past behavior.

He pointed out, however, that the North has taken some "positive measures" recently, apparently referring to the release of three American prisoners and the purported demolition of its nuclear test site in Punggye-ri.

"We can look forward to a bright future and we must seize this opportunity," he stressed.

Japan's defense chief expressed support for the upcoming summit between North Korean leader Kim Jong-un and US President Donald Trump.

He urged the two sides to address the issues of the North's ballistic missiles and abduction of Japanese nationals decades ago.

According to a joint press statement summing up the outcome of the gathering, the military leaders voiced the hope that the planned summit will contribute to "comprehensively resolving pending security and humanitarian issues."

They welcomed the North's removal of its nuclear-testing site following the announcement of a halt to its ballistic missile launches.

They pointed out that the security and prosperity of North Korean people will be "greatly improved" if Pyongyang faithfully abides by international obligations.

The Singapore meeting was the first three-way talks between them since last October, when they gathered in Clark, the Philippines, for the ASEAN Defense Ministers' Meeting-Plus. (Yonhap)