Work on disabling North Korea's main nuclear complex will begin by early next week, according to US officials.
The US envoy said disablement was only the start of the process
"We would like to start as soon as possible," said Sung Kim, one of a team of experts who travelled to North Korea on Thursday to oversee the process.
Pyongyang agreed to the disabling of the Yongbyon site in exchange for aid and security guarantees.
It pledged to shut its main facilities and give details of its nuclear programme by the end of this year.
The agreement came after many rounds of six-party negotiations in Beijing involving China, the US, Japan, Russia and the two Koreas.
The chief US envoy to North Korea, Christopher Hill, said he was confident the overall plan would be effective.
He added that he was "very satisfied" with progress made in preparatory talks on Wednesday with his North Korean counterpart, Kim Kye-gwan.
Kim Kye-gwan confirmed that "at this stage, there are no major differences in opinion".
In all, it is expected that two teams of about nine US technicians and experts will begin work at the Yongbyon site, which has been at the centre of the controversy over North Korea's nuclear programme.
Working in two or three-week rotations over about two months, they will slowly disable the plant, which produces weapons-grade plutonium.
"It will be a combined effort, with North Korean help and our experts supervising and co-ordinating," said Sung Kim, director of the US state department's Korean affairs team.
Sung Kim will head the first team, which arrived in North Korea on Thursday.
Mr Hill said work on the facility was likely to start later this week, although Sung Kim said it would probably not begin until next week.
"We are very satisfied that we have an overall plan that will be effective and will provide the disablement that we need, with the understanding that disablement is not the last stage - and I cannot emphasise that enough," said Mr Hill.