"We're not going to do anything unless he gives us a reason to do something. So our goal is not to start a fight," Haley said on NBC's "Today" in response to a question if the US is seriously considering a preemptive strike against the North.

Asked what such a reason could be, the envoy said, "if you see him attack a military base, if you see some sort of intercontinental ballistic missile. Then obviously we're going to do that."

"But right now, we're saying, 'Don't test, don't use nuclear missiles, don't try and do any more actions' and I think he's understanding that. China is helping us really put that pressure on," Haley said.

Asked again if the US would take military retaliation if the North tests an ICBM or a nuclear device, Haley said, "I think then the president steps in and decides what's going to happen."

Tensions with North Korea have escalated again in the run-up to Tuesday's anniversary of the founding of the North's military amid fears Pyongyang could mark the holiday with a nuclear test in what would be a brazen defiance of the US and the international community.

Adding to the tensions is the North's detention of a third American citizen last week.

"What we've said from the beginning and what I'll continue to say is the United States is not looking for a fight. So don't give us a reason to have one," the envoy said.

Haley said the US is working closely with China to rein in the North.

"Kim Jong-un is starting to flex his muscles because he feels the pressure. Last week, the Security Council unanimously condemned what North Korea's doing with their testing. China has been considerably helpful in putting pressure on him," Haley said, referring to last week's Security Council press statement unanimously condemning the North's latest missile launch.

"I think he's just trying to show his strength to the people of his country, but it's not going to work," she said.

China has "really been our partner in trying to make sure that we hold him at bay," the envoy said.

"I think it's a new day when you've got China and the United States working together on a statement to condemn North Korea.

They've put pressure on him. He feels it. That's why he's responding this way and I think it is a different day," she said.

On the latest US detainee in the North, Haley said that the US will do everything to get detainees released.

"It's very hard to get information out of North Korea, obviously, but we're doing everything that we can," she said. "This makes three detainees that they have right now. And again, this is him trying to pick a fight with us and we're going to have to do is work very hard to find out information and see what we need to do to get these three out safely." (Yonhap)