Rex Tillerson
Rex Tillerson Reuters

U.S. Secretary of State Rex Tillerson expressed confidence on Tuesday that Washington is doing all it can to force North Korea to negotiate its nuclear disarmament.

But, even as he vowed to pursue his diplomatic strategy "until the first bomb drops", he also warned that the U.S. military stands ready to act if necessary, according to comments quoted by AFP.

Tillerson added that if diplomacy and sanctions fail and the fighting erupts, it will have been a personal failure of his efforts to resolve the crisis.

"So we need the DPRK to come to the table for talks. We're ready to talk any time they'd like to talk," he said in a speech to the Atlantic Council policy forum, referring to North Korea by its official acronym.

"But they have to come to the table, and they have to come to the table with a view that they need to make a different choice," he added, according to AFP.

Tillerson insisted Pyongyang must show it is ready to consider surrendering its bombs.

Tensions on the Korean peninsula have risen markedly in recent months after North Korea’s latest missile and nuclear tests, conducted in defiance of international pressure and United Nations resolutions.

Most recently, North Korea launched a Hwasong-15 missile, a new type of intercontinental ballistic missile (ICBM) which officials said can fly over 13,000 km (8,080 miles).

Pyongyang said following the launch that it had test-fired its most advanced missile, putting the U.S. mainland within range.

The isolated country also declared itself to be "a responsible nuclear power" and said its nuclear weapons were developed in order to provide protection from "the U.S. imperialists’ nuclear blackmail policy and nuclear threat."

Last week, North Korea’s foreign ministry declared that the outbreak of war on the Korean peninsula was “an established fact”, citing large military drills being carried out by the United States and South Korea and U.S. threats of a preemptive war against Pyongyang.

Washington has pledged to deliver a denuclearized Korean peninsula, but the strategy hinges on China maintaining pressure and North Korean leader Kim Jong Un agreeing to talk.

"We want them to make the right choice, which is to stop and say: 'Let's sit down to talk about it,'" Tillerson said in an earlier speech to staff.

"Because if they keep going, they can cross a point at which there's nothing left for us in the diplomatic community to do," he warned.

"We've done everything we can do, as we don't want to get to that point," Tillerson added, stressing that he works closely with U.S. Secretary of Defense Jim Mattis.

"And I've said to my partner Secretary Mattis many times: 'If we get there, I've failed. And I don't want to fail,'" he promised.