A former US general has warned war with North Korea is even closer.
Former US Vice Chief of Staff Jack Keane spoke to Fox News about the threat of conflict with leader Kim Jong-un.
"We are much closer to war than we have ever been before with North Korea," he says.
"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."
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Last week US President Donald Trump warned Mr Kim that the US has a bigger and more powerful nuclear button than North Korea.
"North Korean Leader Kim Jong Un just stated that the 'Nuclear Button is on his desk at all times.' Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!" Mr Trump said on Twitter.
It came in response to Mr Kim saying "a nuclear button is always on my desk" during a speech on New Year's Day.
During Mr Kim's speech, he said the United States in within range of North Korea's nuclear weapons, and that is "a reality, not a threat".
"This year we should focus on mass producing nuclear warheads and ballistic missiles for operational deployment. These weapons will be used only if our security is threatened."
Mr Keane says Central Intelligence Agency director Mike Pompeo is warning North Korea could be ready to strike the US within months.
"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," he told Fox News.
"If that's the case then we have got a showdown coming here pretty soon."
However Mr Keane says war won't begin without a noticeable 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," he says.
"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."
The Trump administration is reportedly also planning on removing constraints on the use of nuclear weapons and developing new low-yield nuclear warheads, according to a former official.
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.
"It doesn't have as much terrible stuff in it as it did originally.
"But it's still bad."