The United States is always open to talks with North Korea, Defense Secretary Mark Esper said, amid growing concern that the communist nation could restart testing of long-range missiles or nuclear weapons amid stalled talks with Washington.

Esper made the remarks during an interview with Fox News aired Sunday (Washington time) when asked what the US would do if North Korea resumes nuclear testing, following a recent statement from the North's UN ambassador that denuclearization is off the negotiating table with the US

"I'm not going to comment on hypotheticals. ... We'll see. I think that talks are always open," Esper said. "I've said, Secretary Pompeo has said, and certainly President Trump has said, we want to sit down, we want to have negotiations, and we want to reach the point where we have denuclearized North Korea."

Esper also said his top priority is to ensure defense readiness, but added, "But my second task is to enable our diplomats."

The interview appears to have been recorded prior to Pyongyang's announcement Sunday that it has conducted a "very important test" at the North's Sohae satellite launching station in the country's northwest region.

The North didn't say what was tested, but the announcement came just days after news reports that the North have shown signs of preparing for a rocket engine test that could possibly be used in its launch of an intercontinental ballistic missile.

Pyongyang has ramped up pressure on the US to meet its demand for a new acceptable negotiating proposal by the end of the year, strongly suggesting that otherwise, it could restart testing of nuclear weapons and ICBMs. (Yonhap)