WASHINGTON (CBSNewYork) — North Korea is threatening to retaliate against the U.S. for sponsoring a UN resolution authorizing tougher economic sanctions against Pyongyang.

As CBS News’ Weijia Jiang reported, Secretary of State Rex Tillerson said the U.S. will negotiate under certain conditions.

North Korea is remaining defiant in the face of the new sanctions. Pyongyang blamed the U.S. for the sanctions and vowed to retaliate “a thousand fold.”

North Korea also insisted it would never give up its nuclear weapons program.

“The best signal that North Korea could give us that they are prepared to talk would be to stop these missile launches,” Tillerson said.

Tillerson has indicated a willingness to negotiate, but conceded that the North Koreans may not actually want a sit-down.

“We have not had extended periods of time where they were not taking some type of provocative action by launching ballistic missiles,” he said.

The new sanctions ban North Korean experts of coal, iron, lead, and seafood – potentially a third of its revenues.

To former U.S. ambassador Nicholas Burns, it is clear that Pyongyang is prioritizing its security over the economy.

“I think Kim Jong-Un, this young leader of North Korea, believes that his possession of nuclear weapons is his ultimate protection against any foe — most especially the United States,” he said.

Georgetown University professor Balbina Hwang is a former State Department specialist on North Korea.

“Sanctions have a spotty history,” Hwang said.

Hwang said years of UN sanctions have failed to stop North Korea.

“Does that mean they won’t work in the future?” Hwang said. “We haven’t tried strict enough sanctions — that’s what the latest sanctions are about.”

Tillerson said the sanctions will not work unless they are enforced, and has called upon China and Russia to help do just that.

U.S. intelligence sources tell CBS News that the North Korean military already appears to be preparing for another missile launch.