US Vice-President Mike Pence threatened on Wednesday to slap the toughest US sanctions ever against North Korea during a visit to Japan.

“I’m announcing today that the United States of America will soon unveil the toughest and most aggressive round of economic sanctions on North Korea ever,” he said in joint remarks delivered with Japanese Prime Minister Shinzo Abe in Tokyo. “We will continue to isolate North Korea until it abandons its nuclear and ballistic missile program once and for all.”

Pence, however, didn’t specify what the new sanctions would be.

Abe, in his remarks, said that he and Pence confirmed on Wednesday that Japan would continue to apply “maximum pressure” on North Korea, in cooperation with Seoul, to counter Pyongyang’s nuclear ambitions.

“We confirmed the necessity of using every possible means to increase pressure as much as possible through coordination between Japan and the United States, and between Japan, the United States and South Korea, to make North Korea change its policies,” Abe said.

Pence is on an Asian tour that will end with him attending the opening ceremony of the Winter Olympics in Pyeongchang, South Korea on February 9.