President Trump lashed out at North Korea on Tuesday in response to reports of a new milestone in its nuclear quest, vowing the rogue regime risks "fire and fury like the world has never seen."

His harsh comments to reporters came hours after The Washington Post, citing a confidential Defense Intelligence Agency report, said North Korea has produced a miniaturized nuclear warhead that can fit inside its missiles.

"North Korea best not make any more threats to the United States," Trump said from the clubhouse at his golf course in Bedminster, N.J. "He has been very threatening beyond a normal state, and as I said they will be met with the fire and fury and frankly power, the likes of which this world has never seen before."

The DIA completed the latest analysis on the miniature warhead in July, shortly after another intelligence assessment that sharply raises the official estimate for the total number of bombs in the communist country’s atomic arsenal.

The warhead breakthrough is considered a crucial advancement on the path to producing a nuclear weapon capable of striking the U.S. mainland, experts said.

“Today is the day that we can definitely say North Korea is a nuclear power," Harry Kazianis, director of defense studies at the Center for the National Interest, told USA TODAY. "There is no more time to stick our heads in the sand and think we have months or years to confront this challenge."

The DIA and Pentagon did not immediately respond to USA TODAY's requests for comment on the report. The State Department declined to comment citing "intelligence matters."

Kazianis said it still is not clear whether North Korea has developed heat shield technology required to allow a missile to leave and re-enter the atmosphere. But he said the U.S. should assume the worst. "Today is truly a sad day indeed," he said.

The DIA 's latest assessment comes against a backdrop of growing international concern regarding North Korea's nuclear and missile testing. North Korea has launched more than a dozen test missiles this year. Concerns were heightened late last month when tests of an intercontinental ballistic missile indicated Pyongyang may be within a year or two of obtaining the technology to reach the U.S. with nuclear missiles.

China, Pyongyang's biggest supporter, on Sunday urged North Korea to halt its testing. That came a day after China and Russia joined with the United States in a unanimous U.N. Security Council vote approving the toughest economic sanctions yet against the increasingly isolated regime.

The sanctions target about a third of North Korea's estimated $3 billion in annual exports. North Korea expressed outrage at the U.N. vote, vowing to launch “thousands-fold” revenge against the United States.

The U.S. has expressed a willingness to work with Korean leader Kim Jong Un. Secretary of State Rex Tillerson said last week that the U.S. was not demanding regime change and was willing to talk with Pyongyang — if the North agrees to abandon its quest for nuclear weapons.

North Korea has repeatedly refused to conduct any negotiations aimed at halting its nuclear progress. Experts on the crisis repeated a call made by the Trump administration in recent months: China, North Korea's top trading partner and protector, must step in.

"Today's news makes clear that much more than these sanctions is required to protect U.S. interests, said Jay Lefkowitz, a former U.S. special envoy on human rights in North Korea. "But if we expect China to really crack down on NK, we need to be serious about what China's interests are."

Kazianis said China must enforce the sanctions and strip North Korea of vital resources used for its militarization.

"If they don’t, we will wake up one morning and discover North Korea has tested a hydrogen bomb or a three-stage ICBM — and that could hit ALL of the U.S. homeland.”