Former U.S. National Security Advisor John Bolton speaks at the Center for Strategic and International Studies September 30, 2019 in Washington, DC.

"He [North Korean leader Kim Jong Un] will do whatever he can to keep a deliverable nuclear weapons capability and to develop and enhance it further. He may try to get relief from international sanctions, he may make some concessions, but under current circumstances, he will never give up nuclear weapons voluntarily," Bolton told an audience at the Center for Strategic and International Studies.

"I think right now we are in a classic standoff with North Korea. They want a piece of something that we should not be prepared to give them," Bolton said of Pyongyang's ambition to maintain an arsenal of nuclear weapons.

In his first public remarks since leaving the Trump administration three weeks ago, John Bolton said Monday that it would be unacceptable for North Korean leader Kim Jong Un to possess nuclear warheads.

WASHINGTON — President Donald Trump's former national security advisor said the United States is in a "classic standoff" with North Korea as Washington seeks to denuclearize the Korean Peninsula.

In his remarks, Bolton took aim at the Trump administration's slow progress in resolving the nuclear threat posed by North Korea and Iran.

"When we say we are in no rush for negotiations, we are in no rush for resolution of this, we are saying to North Korea and Iran, 'Take your time, keep going, you've got more time to plan, to test, to produce, to deploy these capabilities.'"

Last month during the Group of 7 meeting, Trump said he was not happy after North Korea launched short-range ballistic missiles but also downplayed the series of tests.

"I'm not happy about it, but again he's not in violation of any agreement," Trump said when asked about the recent string of tests during a bilateral meeting with Japanese Prime Minister Shinzo Abe in Biarritz, France.

"I discussed long-range ballistic, and that he cannot do, and he hasn't been doing it, and he hasn't been doing nuclear testing. He has done short-range, much more standard missiles; a lot of people are testing those missiles, not just him. We are in the world of missiles, folks, whether you like it or not," he added.

Trump's comments came on the heels of what appeared to be two short-range ballistic missiles launched from North Korea's eastern coast. The launch was the latest in a series of tests in recent weeks amid stalled denuclearization talks.

In his address to the Washington think tank, Bolton warned that the Trump administration's acceptance of Kim's short-range missile tests still presented a threat to the United States.

"The testing of shorter-range ballistic missiles that we've seen in recent months doesn't give us any reason to think that those are not threatening," Bolton said.

"The capabilities, the technology, things like the maneuverability of close-range or short-range ballistic missiles can be by definition adapted to longer-range ballistic missiles," he warned.

North Korea, the only nation to have tested nuclear weapons this century, spent most of Trump's first year in office perfecting its nuclear arsenal.

The newest member of the world's exclusive nuclear weapons club has stopped testing of its nukes for now as the U.S. and international community offer the possibility of relief from crippling economic sanctions.