North Korea must stop conducting nuclear tests before the United States would enter into any talks with the isolated Pyongyang regime, US ambassador to the United Nations Nikki Haley said Sunday.

"They have to stop testing. They have to be willing to talk about banning their nuclear weapons. Those things have to happen," she said Sunday, one day after President Donald Trump indicated he would be open to speaking directly with North Korean leader Kim Jong-Un.

"This is going to be phases. This isn't going to happen overnight, as we've seen, but it's a dangerous situation," Haley said on ABC's "This Week."

Trump's latest remarks appeared to be a pivot away from his often-bellicose rhetoric on North Korea and Kim, but Haley said there was "no turnaround" in the US stance.

"What he has basically said is, yes, there could be a time where we talk to North Korea but a lot of things have to happen before that actually takes place," she said.

Trump has jumped between taking a provocative approach toward North Korea -- including trading personal insults with Kim and threatening to destroy his regime -- and calling for a peaceful resolution.

Haley said Trump's hot-and-cold approach was "very clear" in sending a message to Pyongyang that "we're not letting up on the pressure."

"I think that (Trump) always has to keep Kim on his toes. It's very important that we don't ever let him get so arrogant that he doesn't realize the reality of what would happen if he started a nuclear war."

In recent months, the North has held multiple missile launches and its sixth and most powerful nuclear test -- purportedly of a hydrogen bomb -- in violation of UN resolutions banning such activity.

North and South Korea are set to hold their first official dialogue in more than two years this week, and are expected to discuss the North's participation in next month's Winter Olympics in South Korea.

"Those two countries have to get along. That's good for the United States that they can at least start getting back into talks," Haley said.

source: AFP