The U.N. nuclear watchdog demanded Friday that North Korea reverse its decision to expel inspectors who have been monitoring the communist nation's nuclear facilities.

The head of the International Atomic Energy Agency said the North's demand would rob the agency of its last means to ensure the facilities are not being used to produce nuclear weapons. He said it worsens the crisis sparked by Pyongyang's decision to revive its long-frozen nuclear complex.

The North removed the IAEA's monitoring seals and surveillance cameras from the complex earlier this week and began moving in fuel rods needed to restart the 5-kilowatt reactor at Yongbyon, north of the capital, Pyongyang.

The Vienna-based agency confirmed Friday that it had received a letter from the North Koreans "requesting the immediate removal of IAEA inspectors." There was no word on when the North wanted the inspectors out.

"Together with the loss of cameras and seals, the departure of inspectors would practically bring an end to our ability to monitor (North Korea's) nuclear program or assess its nature," IAEA head Mohamed ElBaradei said in a statement. "This is one further step away from defusing the crisis."

ElBaradei sent a response to North Korea's atomic energy chief, Ri Je Son, urging the North to allow the inspectors to remain and to install new seals and cameras at the Yongbyon complex.

The IAEA has been monitoring the complex since the North closed it in 1994 under an agreement that aimed to ensure that the isolated state does not divert nuclear materials to make weapons.

The IAEA normally has two inspectors in North Korea. They are international experts, based in Vienna, and travel to North Korea for stints that last about two weeks. On Friday, three inspectors were in the country because of an overlap in a routine rotation, IAEA spokeswoman Melissa Fleming said.

The North Korean decision to expel the agency inspectors was first announced earlier in the day by that country's official news agency, KCNA.

The news agency also reported that North Korea would reactive a reprocessing laboratory at the facility where plutonium can be extracted from spent fuel rods. Plutonium can be used to make atomic bombs. The IAEA statement did not address that matter.

North Korea already holds 8,000 spent fuel rods. U.S. officials say that the spent fuel rods contain enough plutonium to make several atomic bombs.

As of Friday, about 2,000 fresh fuel rods had been moved to a storage facility in the reactor, Fleming said. That was 1,000 more rods than had been moved a day earlier.

The reactor needs 8,000 rods to be started, Fleming said, adding that no work appeared to have been done Friday because of a North Korean holiday. She had no information on how long it would take to move the 6,000 rods still needed to start the reactor.