Responding to Seoul's offer of high-level talks with Pyongyang, Ambassador Nikki Haley told reporters: "We won't take any of the talks seriously if they don't do something to ban all nuclear weapons in North Korea."
"We consider this to be a very reckless regime. We don't think we need a band-aid and we don't think we need to smile and take a picture.
"We think we need to have them stop nuclear weapons and they need to stop it now," she said, warning: "We will never accept a nuclear North Korea."
North Korea's race to build an intercontinental ballistic missile capable of hitting the United States with a nuclear warhead has prompted stepped up UN sanctions -- and raised fears of a nuclear conflict.
South Korea extended the offer of talks, to take place January 9, after the North's leader Kim Jong-Un called for better relations and said his country might attend the Winter Olympics.
President Donald Trump held up the development as proof the campaign of pressure was having a "big impact."
And when asked to comment on the prospect of direct Korean talks -- and whether such a development could upset its strategy on the crisis -- the White House said its policy remained unchanged.
"Our goals are the same and we share that with South Korea."
Washington has spearheaded the international push to sanction North Korea at the United Nations, which last year slapped three rafts of economic sanctions on the regime, targeting its oil, coal, iron, fisheries and textile sectors.
Responding to reports that Pyongyang may be preparing another missile test, Haley warned any such move would expose Kim's regime to further sanctions.
"I hope that does not happen. But if it does, we must bring even more measures to bear on the North Korean regime."
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.