During his stay at his Bedminster, N.J., golf club on Aug. 8, President Trump said North Korea "will be met with fire and fury like the world has never seen" if they continue making nuclear "threats." (Reuters)

BEDMINSTER, N.J. -- President Trump on Tuesday issued a stern warning to North Korea, saying that if its threats to the United States continue, the outcast nation will be “met with fire and fury like the world has never seen.”

Trump comments came as North Korea spurned a new round of sanctions approved by the United Nations Security Council and pledged to continue to press forward with development of nuclear weapons that could reach the U.S. mainland.

Appearing at an event at his Bedminster, N.J., golf club, where Trump is on a 17-day “working vacation,” he said that “North Korea best not make any more threats to the United States.”

“They will be met with fire and fury and frankly power, the likes of which this world has never seen before,” Trump said, as his administration faces one of its most serious foreign policy challenges of his presidency.

Speaking of North Korean leader Kim Jong Un, Trump said “he has been very threatening beyond a normal state.”

The Washington Post on Tuesday reported that North Korea has successfully produced a miniaturized nuclear warhead that can fit inside its missiles, crossing a key threshold on the path to becoming a full-fledged nuclear power, according to a confidential assessment by U.S. intelligence officials.

Trump’s warning Tuesday further raises the stakes for the U.S. president and other world leaders, who face limited options in dealing with North Korea’s aggression.

On Twitter on Tuesday, Trump suggested progress is being made with the cooperation of China and Russia, both of which supported the Security Council resolution offered by the United States over the weekend.

“After many years of failure, countries are coming together to finally address the dangers posed by North Korea,” Trump said. “We must be tough & decisive!”

There was no sign at a major Asian security conference in Manila that the sanctions, hailed by Trump as a ­foreign policy achievement, would succeed where past efforts have failed in trying to persuade North Korea to give up its nuclear weapons.

North Korean Foreign Minister Ri Yong Ho told diplomats that his country will never negotiate away what he called a rational “strategic option” against the threat of attack from the United States.

“We will, under no circumstances, put the nukes and ballistic rockets” up for negotiation, he said in prepared remarks, adding that the entire United States is within range of its missiles.

Ri dismissed the U.N. sanctions approved Saturday as illegal, appearing to rule out talks that the Trump administration, in a diplomatic partnership with China and Russia, is offering North Korea as a way out of its economic and diplomatic pariah status.

The U.S. assessment about North Korea’s progress in producing a miniaturized nuclear warhead are likely to deepen concerns about an evolving North Korean military threat that appears to be advancing far more rapidly than many experts had predicted.

U.S. officials last month concluded that Pyongyang is also outpacing expectations in its effort to build an intercontinental ballistic missile capable of striking cities on the American mainland.

While more than a decade has passed since North Korea’s first nuclear detonation, many analysts believed it would be years before the country’s weapons scientists could design a compact warhead that could be delivered by missile to distant targets. But the new assessment, a summary document dated July 28, concludes that this critical milestone already has been reached.

Trump’s comments Tuesday came at an event focused on the country’s opioid crisis. After he finished opening remarks on that subject, he was asked by a reporter about North Korea. Trump sat back in his seat, arms folded and looked straight into the cameras as he made his comments.

Wagner reported from Washington. Carol Morello and Anne Gearan in Washington contributed to this report.