The US has approved a plan to disable North Korea's main nuclear facilities by the end of the year.
North Korea closed its main nuclear reactor, in Yongbyon, in July
A state department spokesman said the US had endorsed the statement, drafted during six-nation talks on Sunday.
The top US negotiator in North Korea said the US would be "heavily" involved in disablement work under the plan.
Pyongyang tested a nuclear device last year but agreed to end its nuclear programme in return for aid. It has already closed its main reactor.
The plan was endorsed as the leaders of North and South Korea met for a historic summit in the North Korean capital, Pyongyang - only the second such meeting since 1945.
State department spokesperson Sean McCormack said US officials had told the Chinese government they backed the draft joint statement, which sets out the second stage of North Korea's denuclearisation process under a deal agreed in February.
Pyongyang is expected to declare and shut down the rest of its nuclear operations in this phase, after closing five facilities - including its main Yongbyon reactor - as part of the first phase in July.
"We studied [the draft statement], examined it and gave our approval to the Chinese," Mr McCormack said.
"I can't speak for the status of the other countries."
AFP news agency quoted the top US negotiator on North Korea, Assistant Secretary of State Christopher Hill, as saying Washington would be "very heavily" involved in North Korea's nuclear disablement as part of the plan.
"There are some undertakings in this agreement which would involve, for example, the issue of various parties, namely the US, participating very heavily in the issue of actual disablement," Mr Hill said.
"So we will anticipate having people on the ground to participate in the disablement, for example."
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No other details of the plan have been released, but Mr Hill said he expects China - which is hosting the six-party talks - to release the approved statement within two days.
Talks have stopped while governments of the six nations - China, Japan, Russia, the US and the two Koreas - consider the draft.
North Korea reportedly wants the statement to acknowledge its goal of being removed from the US list of countries that sponsor terrorism.
But the US has said it will only do so after Pyongyang had shut down its entire nuclear programme.