Austria ? A senior official from the U.N. nuclear watchdog left for North Korea on Sunday to discuss how the agency’s inspectors would monitor and verify the shutdown of the Yongbyon nuclear reactor.

Olli Heinonen, the International Atomic Energy Agency’s deputy director general for safeguards, was due to arrive Tuesday in Pyongyang for a five-day visit, along with three colleagues.

North Korea, which expelled U.N. inspectors in late 2002, announced last week that it invited a “working-level delegation” to discuss procedures for shutting down the plutonium-producing facility.

“The purpose of this trip is now to go negotiate the details on behalf of the IAEA and verification of the monitoring and closing-down of the Yongbyon facility,” Heinonen told reporters at Vienna Airport.