"Our goal is a peaceful settlement," he added, noting the Trump administration's "maximum pressure" campaign, which involves increasing economic and diplomatic sanctions against Pyongyang. "But we have to face the fact that this is an existential -- potentially existential problem for the United States."

Tensions heightened last year as the defiant regime conducted its sixth and most powerful nuclear test as well as three tests of intercontinental ballistic missiles capable of striking the US.

President Donald Trump has threatened to "totally destroy" the regime if necessary, sparking fears of an armed conflict on the Korean Peninsula. Meanwhile, South and North Korea last month held their first high-level talks in years, leading to the North's participation in the Winter Olympics currently under way in the South's PyeongChang.

Amid the apparent thaw, the US has also expressed a willingness to engage Pyongyang to emphasize its determination to denuclearize the peninsula.

Coats described the North as the "most volatile and confrontational" weapons of mass destruction threat this year.

"We expect to see North Korea press ahead with additional missile tests this year, and its foreign minister has threatened an atmospheric nuclear test over the Pacific," he said.

Mike Pompeo, director of the Central Intelligence Agency, told the same hearing "a test like that would certainly further unite the region." (Yonhap)