CIA director Mike Pompeo has said North Korea is a few months away from perfecting its nuclear weapons capabilities.

“They are close enough now in their capabilities that from a US policy perspective we ought to behave as if we are on the cusp of them achieving” their objective of being able to strike the United States, Pompeo told a national security forum in Washington.

But he said there was a difference between having the ability to fire a single nuclear missile and the capability of producing large amounts of fissile material and developing an arsenal of such weapons.

Pompeo said intelligence on North Korea was imperfect and “when you’re now talking about months, our capacity to understand that at a detailed level is in some sense irrelevant”, he said.

“We are at a time where the president has concluded that we need a global effort to ensure Kim Jong-un doesn’t have that capacity,” Pompeo told the forum, organised by the Foundation for Defense of Democracies thinktank.

He said China had done more than expected to reduce trade with its wayward ally but could do more. Beijing had also communicated around the world it is intent on helping the US resolve the issue.

“We all want to resolve this” without resorting to military activity, the CIA chief said, but added President Donald Trump was prepared to use force if necessary to ensure Kim “doesn’t have the capacity to hold America at risk”.

North Korea has accelerated its weapons tests. In July it twice launched a long-range missile that could potentially reach the US mainland. In September it conducted its most powerful atomic explosion yet. This week its UN envoy said nuclear war could break out at any moment.

Dire threats traded by Trump and Kim have further stoked fears of war.

The former CIA Director John Brennan has voiced concerns about Trump’s tweets and said the prospects of a military conflict on the Korean Peninsula “are greater than they have been in several decades”.

“I don’t think it’s likely or probable, but if it’s a one in four or one in five chance, that’s too high,” Brennan said at Fordham University in New York.