North Korea is on track to disable its nuclear program by the end of this year as its differences with the United States have mostly been resolved, a U.S. envoy said on Tuesday.

As a team of atomic experts prepared to travel to North Korea, U.S. negotiator Christopher Hill was upbeat as he arrived in Beijing for talks with his North Korean counterpart, Kim Kye-gwan.

Hill had previously spoken of problems with North Korea over defining the depth of disablement.

"There are some issues that need to be finalized, but we're beyond the issue that I described a month ago where we wanted to do more and they wanted to do less," Hill told reporters. "I think we're okay on that point."

North Korea agreed earlier this month to disable its nuclear program by the end of 2007, following six-way talks that group the two Koreas, the United States, Japan, Russia and host China.

North Korea also pledged to make a full declaration of its atomic programs by the end of the year, and Hill said discussions on that would begin in the next few weeks.

In exchange, the impoverished and isolated country will receive energy aid, as well as better relations with Washington. The United States will also move toward taking North Korea off a U.S. terrorism blacklist.

The moves follows a breakthrough February deal under which North Korea -- which tested a nuclear device last year in defiance of international warnings -- shut down and sealed its Yongbyon nuclear plant and admitted U.N. atomic inspectors.

An expert team will head to the North on Thursday, to push forward the process of disablement, Hill said.

But there are still thorny issues ahead, including the question of whether North Korea has a uranium enrichment program.

Hill said he would also discuss proliferation with North Korea, following reports that it supplied nuclear know-how to Syria.

"Obviously as we go forward, we need to go forward in a spirit of increasing openness and trust, and to achieve that, we need to know if things have happened in the past, and be assured that if things have happened in the past they won't happen in the future," he said.

Hill is to meet Kim on Wednesday and hold talks with the Chinese side, before flying to Seoul and Tokyo.

Chinese Foreign Ministry spokesman Liu Jianchao said Kim would also hold talks with Chinese officials.

A huge baseball fan, Hill will also attend a reception with baseball great Cal Ripken, who is in Beijing as a goodwill ambassador for the United States.

(Additional reporting by Benjamin Kang Lim)