SEOUL, South Korea (AP) — North Korea vowed Monday to bolster its nuclear arsenal and gain revenge of a “thousand-fold” against the United States in response to tough U.N. sanctions imposed following its recent intercontinental ballistic missile tests.

The warning came two days after the U.N. Security Council unanimously approved new sanctions to punish North Korea, including a ban on coal and other exports worth over $1 billion. The U.S. ambassador to the U.N., Nikki Haley, called the U.S.-drafted resolution “the single largest economic sanctions package ever leveled against” North Korea.

In a statement carried by the North’s state-run Korean Central News Agency, North Korea’s government said the sanctions were a “violent infringement of its sovereignty” that was caused by a “heinous U.S. plot to isolate and stifle” the country.

“We will make the U.S. pay by a thousand-fold for all the heinous crimes it commits against the state and people of this country,” the statement said.

The North said it would take an unspecified “resolute action of justice” and would never place its nuclear program on the negotiating table or “flinch an inch” from its push to strengthen its nuclear deterrence as long as U.S. hostility against North Korea persists.