Japanese Defense Minister Itsunori Onodera, Korean Defense Minister Kim Kwan-jin and U.S. Defense Secretary Chuck Hagel met last weekend in Singapore to discuss the security situation on the Korean Peninsula.
A joint statement from the three defense leaders said there was a common view that a North Korean missile launch in December and the February nuclear test were considered provocative actions.
"(The tests) are serious threats that undermine not only the peace and stability of the Korean Peninsula but also those of Northeast Asia and around the world," the statement said.
Talks between the Koreas, China, Japan, Russia and the United States were suspended in 2008. North Korea has since conducted a series of underground nuclear tests.
Onodera, Kim and Hagel said trilateral cooperation was vital to ensure the region is peaceful despite the North Korean threat.
South President Park Geun-hye is to visit Chinese President Xi Jinping in Beijing in late June to discuss the regional security situation. Xi is also to meet with U.S. President Barack Obama this week in California.