Washington's new diplomatic overture comes after Pyongyang said it had successfully tested an advanced intercontinental ballistic missile.
US Secretary of State Rex Tillerson on Tuesday has offered to begin direct talks with North Korea without pre-conditions, backing away from a key US demand that Pyongyang must first accept that giving up its nuclear arsenal would be part of any negotiations.
Tillerson's new diplomatic overture comes nearly two weeks after North Korea said it had successfully tested an advanced intercontinental ballistic missile that put the entire United States mainland within range of its nuclear weapons.
"Let's just meet," Tillerson said in a speech to Washington's Atlantic Council think tank on Tuesday.
The White House later issued an ambiguous statement that left unclear whether President Donald Trump - who has said Tillerson was wasting his time pursuing dialogue with North Korea - had given his approval for the speech.
"The president's views on North Korea have not changed," the White House said. "North Korea is acting in an unsafe way ... North Korea's actions are not good for anyone and certainly not good for North Korea."
TRT World's Nafisa Latic has this report.
Ahead of Tillerson's speech, North Korean leader Kim Jong-un vowed to develop more nuclear weapons while personally decorating scientists and officials who contributed to the development of Pyongyang's most advanced ICBM, according to North Korean state media on Wednesday.
Kim said on Tuesday the scientists and workers would continue manufacturing "more latest weapons and equipment" to "bolster up the nuclear force in quality and quantity", the KCNA news agency reported.
Sec Tillerson: Takes strong partnerships to counter prospect of a nuclear #DPRK. @POTUS' first policy was to end era of strategic patience & begin era of strategic accountability - our policy is the complete and verifiable denuclearization of the #Korean peninsula. #ACKoreaForum pic.twitter.com/uaK5mpdinR— Department of State (@StateDept) December 12, 2017
'Period of quiet'
While reiterating Washington's long-standing position that it cannot tolerate a nuclear-armed North Korea, Tillerson said the United States was "ready to talk any time they're ready to talk", but there would first have to be a "period of quiet" without nuclear and missile tests.
UN political affairs chief Jeffrey Feltman, who visited Pyongyang last week, said senior North Korean officials did not offer any type of commitment to talks, but he believes he left "the door ajar".
"Time will tell what was the impact of our discussions, but I think we have left the door ajar and I fervently hope that the door to a negotiated solution will now be opened wide," Feltman told reporters after briefing the UN Security Council on Tuesday.
But not everyone is ready for talks.
DPA chief Jeffrey Feltman ends visit to the #DPRK, says time is of the essence in finding a diplomatic solution to the dangerous situation in the Korean Peninsula. Readout here: https://t.co/wF1k1uCkv0— UN Political Affairs (@UN_DPA) December 9, 2017
Cooperation with US over Pyongyang
Japan has advocated a strategy of pressuring North Korea through sanctions to give up its nuclear weapons. Tokyo and Washington are in "100 percent" agreement about that stance, Chief Cabinet Secretary Yoshihide Suga said on Wednesday when asked about Tillerson's comments.
A former Japanese diplomat said that, while a diplomatic solution was the "only acceptable solution", now was not the time for talks.
"We have to see the effects of sanctions on life in North said.
"I heard that they are having a serious impact on everyday life. Let's wait and see. If we were to hint anything for dialogue, we'd be losing clout," he said.
South Korea continued with its military exercises with the United States to check military readiness, exercises the North describes as preparation for war. The South's army said separately on Wednesday it conducted a successful air-to-air missile firing drill from Apache helicopters.
US talks to China
Tillerson also disclosed the US had been talking to China about how to secure North Korea's nuclear weapons in the event of a collapse of the government in Pyongyang.
He said Beijing had been given assurances that if US forces had to cross into North Korea they would pull back across the border into the South.
However, he made clear that the US wants to resolve the North Korea standoff through peaceful diplomacy and, in terms far more tempered than Trump's recent threats against Pyongyang, offered to hold exploratory talks.
"We can talk about the weather if you want. We can talk about whether it's going to be a square table or a round table," he said. "Then we can begin to lay out a map, a road map, of what we might be willing to work towards."
Tillerson - whose influence has appeared to wane within the administration - said Trump "has encouraged our diplomatic efforts".
Trump said on Twitter in October that Tillerson was "wasting his time trying to negotiate with Little Rocket Man", using his derisive nickname for Kim.
I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man...— Donald J. Trump (@realDonaldTrump) October 1, 2017
North Korea, for its part, has made clear that it has little interest in negotiations with the United States until it has developed the ability to hit the US mainland with a nuclear-tipped missile, something most experts say it has still not proved.
Tillerson also said the United States was working to tighten enforcement of international sanctions against North Korea, especially further measures that China can apply, and that Washington had a full menu of military options if such a response was needed.
Daryl Kimball, executive director of the non-partisan Arms Control Association, said Tillerson's proposal was overdue but that "in order to get to such talks going, the US side as well as North Korea must demonstrate more restraint".