North Korea is able to mount a miniaturised nuclear warhead on a missile, according to a senior US military official.
However, the official, speaking to reporters on condition of anonymity, said that Kim Jong Un’s regime had not yet worked out the re-entry technology necessary for longer range strikes.
Reuters quoted the official as saying:
"I think they could mate a warhead with a delivery device. They're just not sure (about) re-entry," said the official. "They're endeavouring to overcome that."
The regime has repeatedly defied UN Security Council sanctions by carrying out nuclear and missile tests.
It has conducted at least four tests just this year, including a thermonuclear bomb test in May.
The 'Dear Leader' has also threatened the South and the United States with nuclear strikes.
Partly in response to the threat, the US has confirmed it will deploy its Terminal High Altitude Area Defense System (THAAD) in South Korea in 2017, despite protest from China.
It is also improving its missile defence systems in Alaska and California to shoot down any incoming missiles in mid-flight.
Earlier this year, Admiral Bill Gortney, who is responsible for defending U.S. airspace, told a Senate panel it was "prudent" for him to assume North Korea had the ability to miniaturise a nuclear weapon and put it on a missile that could target the United States.
US President-elect Donald Trump has said he would hold talks with Kim in an attempt to halt their nuclear programme.