North Korea has successfully developed a miniaturized nuclear warhead that can fit inside one of its intercontinental ballistic missiles, a key step in the rogue regime’s ambition to become a nuclear power, a report on Tuesday said.

The findings were contained in a study by the Defense Intelligence Agency, the Washington Post reported.

“The IC [intelligence community] assesses North Korea has produced nuclear weapons for ballistic missile delivery, to include delivery by ICBM-class missiles,” the newspaper reported, citing an assessment from the DIA completed last month.

That report follows another government study that calculates that North Korean President Kim Jong Un’s regime now controls as many as 60 nuclear weapons.

The findings show that Pyongyang’s efforts to develop a long-range missile capable of carrying a nuclear weapon with enough range to strike the US mainland is progressing more rapidly than experts had predicted, the newspaper said.

In January, President Trump said he wouldn’t allow North Korea to cross the nuclear threshold.

“North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the U.S. It won’t happen!,” he wrote on Twitter on Jan. 2.

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Since then the White House has flexed its military muscle by dispatching warships to the waters off the Korean peninsula in April and sent two B-1 bombers to fly over South Korea after North Korea’s most recent ICBM launch on July 28 in a show of force.

He has also pressured China, North Korea’s main trading partner, to pressure Kim to corral his weapons programs, but has been frustrated by what he considers their lack of effort.

US Ambassador to the United Nations Nikki Haley in an interview called newly imposed UN sanctions against North Korea a “gut punch” and warned the regime of possible military action if it continues developing weapons.

“What I will tell you from the United States’ perspective, we’re prepared to do whatever it takes to defend ourselves and defend our allies,” Haley told CNN on Sunday.

National Security Adviser H.R. McMaster also said the US could launch a “preventative war” against North Korea.

“If they had nuclear weapons that can threaten the United States, it’s intolerable from the President’s perspective. Of course, we have to provide all options to do that, and that includes a military option,” he said in an interview Saturday on MSNBC.

But military experts say any preemptive strike against Kim could unleash a counter attack that could result in hundreds of thousands of casualties in South Korea, where the US has 30,000 troops stationed.

Secretary of State Rex Tillerson has left the door open for a diplomatic solution, but only if North Korea ceases test firing its missiles.

The United Nations Security Council voted unanimously on Saturday to impose severe economic sanctions on North Korea for launching two intercontinental ballistic missiles in July.

The ban on exports of coal, iron and seafood products was expected to cost Kim’s government about $1 billion a year and is intended to starve the country’s weapon development program.

But North Korea, which has tested 14 rockets this year, appeared unbowed in light of the mounting global pressure.

The regime said it would unleash “thousands-fold” revenge against the US for the sanctions.

“There is no bigger mistake than the United States believing that its land is safe across the ocean,” Kim government warned, according to state-run media.

With wires