Final warnings: US on verge of war with N Korea

President Donald Trump is preparing for a "showdown" with North Korea as the US draws closer to nuclear war with the rogue state, a retired US general has warned.

Former US Vice-Chief of Staff Jack Keane told Fox News that Trump has pledged to "take care" of Kim Jong-un's ruthless regime.

He warns that the US is "absolutely" at its closest it has ever been to war with North Korea.

"We are much closer to war than we have ever been before with North Korea.

"Yes, we are because this administration is determined - unlike the two previous administrations, actually three - this administration is determined not to let North Korea threaten the American people with nuclear weapons.

"They're not going to let that happen.

"Mike Pompeo reaffirmed once again that we are only months away from North Korea reaching their final technological objective of nuclearising ICBMs capable of re-entry from outer space.

"If that's the case then we have got a showdown coming here pretty soon."

According to the New York Times, security experts noted, "There is no reasonable military option for restraining North Korea that would not involve unacceptable loss of life."

The Atlanta-based Centers for Disease Control and Prevention scheduled a "Public Health Response to a Nuclear Detonation" in January 16 with government officials to inform the public about what preparations have been made.

"While a nuclear detonation is unlikely, it would have devastating results and there would be limited time to take critical protection steps," the group said.

"Despite the fear surrounding such an event, planning and preparation can lessen deaths and illness. For instance, most people don't realize that sheltering in place for at least 24 hours is crucial to saving lives and reducing exposure to radiation. While federal, state, and local agencies will lead the immediate response efforts, public health will play a key role in responding."

North Korea's most recent missile test took place on November 29, and the regime said the Hwasong-15 missile flew 590 miles during its 53-minute flight before landing in the sea near Japan.

The warning comes just a week after Kim Jong-un stated that "a nuclear button is always on my desk" during a speech on New Year's Day.

He also said that North Korea has weapons capable of reaching the US and that war is "a reality, not a threat".

Despite multiple threats from both Trump and Kim Jong-un, Keane says war won't begin without a clear military build-up and plans to protect civilian populations.

"If war is imminent we would be seeing air, sea and ground deployments taking place. Some of them we could not hide.

"Secondly, we would likely be providing some warning to the hundreds of thousands of Americans who are in South Korea to include the families of our soldiers that are there giving them some advice about whether they should evacuate or not.

"So none of those things are taking place yet."

Jon Wolfsthal, who worked for former president Barack Obama, has seen drafts of the Pentagon's new nuclear posture review and says the plans are "bad".

"What I've been told by the people who wrote the thing was what they were trying to do was to send a clear deterrent message to Russians, the North Korean and the Chinese," he told the Guardian.

In an effort to stop the rogue nation, the UN Security Council imposed sanctions on North Korea following its continued missile testing.