North Korea 'only months away' from US strike: diplomat claims

North Korea may be only months away from being able to strike the United States, the US disarmament ambassador says.

A North Korean missile test in August 2017. Source: AAP

North Korea may be only months away from being able to strike the United States with a nuclear-tipped ballistic missile and its atomic weapons program must be shut down, a senior US disarmament official says.

US disarmament ambassador Robert Wood, addressing the UN-sponsored Conference on Disarmament in Geneva, also warned that arsenals in China and Russia were expanding.

"Russia, China and North Korea are growing their stockpiles, increasing the prominence of nuclear weapons in their security strategies, and - in some cases - pursuing the development of new nuclear capabilities to threaten other peaceful nations," he said.

North Korea "may now be only months away from the capability to strike the US with nuclear-armed ballistic missiles".

North Korea has defied years of multilateral and bilateral sanctions with a weapons program aimed at developing nuclear-tipped missiles capable of hitting the US.