WASHINGTON — The U.S. will not move to ease economic sanctions on North Korea until it is confident that the nuclear weapons threat from Pyongyang has been “substantially reduced,” Secretary of State Mike Pompeo said on Thursday.

Pompeo didn’t elaborate, but his comment seemed to leave open the possibility that sanctions relief was possible short of complete and verifiable denuclearization of the Korean Peninsula.

Pompeo told NBC’s “Today” that he hopes North Korean leader Kim Jong Un will make good on his pledge to give up his nuclear weapons during his second meeting with President Donald Trump next week in Vietnam.

But a senior administration official said the U.S. is still not sure if North Korea has decided to give up its nuclear weapons. Asked if North Korea was negotiating in good faith, the official said the nations are in a genuine negotiation, and it will take time to “tease out” exactly what is Kim’s full commitment.

The official, who is familiar with the talks and spoke only on condition of anonymity, also said that reducing the 28,500 U.S. troops stationed in South Korea has not been a topic of the talks.

There has been discussion, however, about using the summit as a venue to declare the end of the Korean War — something that Kim has sought. The fighting ended with an armistice in July 1953. That armistice has yet to be replaced with a peace treaty, leaving the peninsula in a technical state of war.

Pompeo said he didn’t want to get into the details about what either side was willing to offer to make progress in the talks.

“The American people should know we have the toughest economic sanctions that have ever been placed on North Korea and we won’t release that pressure until such time as we’re confident we’ve substantially reduced that risk,” Pompeo said, adding that he hopes the two leaders will take a “truly historic step forward” at their meeting in Hanoi.