MANILA - The Philippines and other Southeast Asian nations play important roles in opposing North Korea's "dangerous" behavior, the United States envoy to Manila said Monday.

The hermit state's behavior has been "a growing concern," and one of the main reasons for US President Donald Trump's trip to the Asia Pacific was to "consult" their allies on cooperation on how to "to deal with this very serious challenge," said Ambassador Sung Kim.

"I think it’s incredibly important that we remain united in the face of North Korea’s provocative, reckless behavior," he told ANC's Headstart.

The Philippines, which chaired the ASEAN the previous year, is "a very important player in the region," said Kim.

"I think the Philippines showed great leadership in unifying the ASEAN region and coming up with a very strong condemnation of North Korea’s provocative behavior," he said.

It is also "very important" that the 10-nation regional bloc joins the international voice in opposing North Korea's behavior, said Kim.

"We need to send a very clear message, a unified message to North Korea that the international community, including the Asia Pacific region, including ASEAN region, will not accept their provocative, dangerous pursuit of the WMD (weapons of mass destruction) capabilities in violation of UN resolutions and their own promises made in the 6-party context," he said.

The North Korea last week test-fired an intercontinental ballistic missile believed to be capable of hitting the US mainland in a new challenge to President Donald Trump.

In response, the largest ever US-South Korea air exercise, involving some 230 aircraft including F-22 Raptor stealth jet fighters, will begin on Monday.

• READ: Korea tensions rise ahead of US-South Korea joint military drill