The top American nuclear negotiator ended his trip to North Korea Friday with little to say about his effort to salvage a derailed disarmament pact and to persuade the country to give up plans to restart its nuclear plant.

Assistant U.S. Secretary of State Christopher Hill was seeking a deal that would allow United Nations monitors back into North Korea to make sure it doesn't have a secret program to enrich uranium for weapons, which would give it another path to make a nuclear bomb.

"I don't want to talk about progress," Hill told reporters in Seoul Friday, saying he must first brief U.S. officials and other countries before releasing any details.

"I don't want to say I'm satisfied [with the talks]," Hill said, adding that he had lengthy and substantive discussions about a nuclear verification system.

South Korea's chief nuclear envoy, Kim Sook, said after meeting Hill there could be a new round of six-way talks to discuss what had happened in Pyongyang.

In late September, the government in Pyongyang ordered the expulsion of UN monitors from its Yongbyon nuclear plant and said it planned to start reactivating it within days.

Hill said Friday he told the North Koreans that the move would be of great concern, but he said he had no information on any further steps the government might have taken to restart the nuclear plant.

The energy-starved country started to disable the Yongbyon plant last November under a deal struck with five regional powers in February 2007.

But then it threatened to restart the plant because the U.S. hadn't yet taken it off its terrorism blacklist, a move that would bring economic and diplomatic benefits to the country.

The U.S. said it would take the country off the terrorism list once a system was in place to verify claims that it's not producing enriched uranium for nuclear bombs.

With files from Reuters