(reuters) -- Talks between the adversaries have long been urged by China in particular, but Washington and its ally Japan have been reluctant to sit down at the table while Pyongyang while it continues to pursue a goal of developing a nuclear-tipped missile capable of hitting the United States.

"Eventually, we don´t rule out the possibility of course of direct talks," Sullivan said in Tokyo after talks with his Japanese counterpart.

"Our focus is on diplomacy to solve this problem that is presented by the DPRK. We must, however, with our allies, Japan and South Korea and elsewhere, be prepared for the worst should diplomacy fail," he said.

Tensions have soared following a series of weapons tests by North Korea and a string of increasingly bellicose exchanges between U.S. President Donald Trump and North Korean leader Kim Jong Un.

(Photo: nytimes)