Diplomats involved in the six-nation North Korean nuclear talks have begun arriving in Beijing to hold what they say is a critical round of negotiations. VOA's Heda Bayron reports from our Asia News Center in Hong Kong.

The lead U.S. negotiator on the North Korea nuclear issue, Christopher Hill, calls this week's round of talks a "very important stage" in the goal of eliminating North Korea's nuclear programs by the end of the year.

External view of the Yongbyon nuclear power plant in North Korea (File)

The U.S. wants a verifiable and complete disabling of North Korea's nuclear programs.

North Korea announced this month that it will dismantle its nuclear programs by the end of this year. This follows an agreement in February with the U.S., China, Japan, Russia and South Korea that Pyongyang will receive 50,000 tons of heavy fuel oil, economic aid and security incentives if it shuts down its nuclear facilities.

On Tuesday, the North Korean envoy to the talks, Kim Kye Kwan, warned that the four-year diplomatic effort could unravel if the U.S. and the other four countries fail to meet their commitments.

The Stalinist state detonated its first test of a nuclear explosion a year ago.

On the way to Beijing Wednesday, Hill met with his Japanese counterpart, Kenichiro Sasae, in Tokyo to discuss the nuclear issue and a possible complication in the talks - Japan's insistence that Pyongyang account for and release Japanese nationals it abducted in the 1970's and '80's.

The government of former prime minister Shinzo Abe, which was replaced Tuesday, had refused to give aid to North Korea under the February agreement because of the abduction issue.

There have been reports that the U.S. may remove the North from its list of states sponsoring terrorism, even before Pyongyang accounts for the Japanese abductees - a move that could upset Tokyo.

In Tokyo, Hill did not mention any such plan.

"I don't want to get into all the issues of how one deals with this in terms of the denuclearization," he said. "But I can just assure you that this is a major priority of ours and that we are working very closely with Japan."

Sasae said Hill has assured Japan that Washington would not strike a deal with Pyongyang at the expense of its relations with Tokyo.

In 2002, Pyongyang returned five of 11 Japanese it has acknowledged abducting and said the others are dead.