North Korea says it has shut down its main nuclear reactor, more than four years after the facility was re-opened. As VOA's Kate Pound Dawson reports from our Asia News Center, a top U.S. diplomat says that is a good first step, but there is more work ahead.

Pyongyang's declaration that it had shut down the Yongbyon reactor came as United Nations inspectors were arriving to examine the facility.

The team from the International Atomic Energy Agency will spend weeks making sure all of the facility is closed, and setting up monitoring equipment to ensure it is not restarted.

Christopher Hill

Assistant U.S. Secretary of State Christopher Hill on Sunday welcomed the news of the shutdown. But he cautioned that more work is needed to end North Korea's nuclear weapons programs.

"We realize how long it took, how long it took, to get here. … I think we have to really work very hard for the additional steps that are necessary," Hill said.

Hill is the lead U.S. negotiator in six-nation talks on ending Pyongyang's nuclear ambitions. He spoke in Tokyo at the end of a visit to prepare for talks this week.

The IAEA visit is the first since the end of 2002, when North Korea abandoned the nuclear Non-Proliferation Treaty, kicked the agency's staff out of the country and restarted the reactor. It did so after the United States said Pyongyang had resumed efforts to build nuclear weapons, despite several international pledges not to.

Since then, the United States, China, Japan, South Korea and Russia have tried to persuade North Korea to abandon its nuclear programs. Those efforts made little progress until this year, and Pyongyang tested a nuclear explosive device last year.

In February, however, North Korea promised to shut down its nuclear facilities in return for energy aid and diplomatic benefits. On Saturday, the first batch of energy aid - more than six thousand tons of fuel oil from South Korea arrived in the impoverished North.

On Wednesday, negotiators from the six nations meet in Beijing to plan the next steps in North Korea's disarmament process.