North Korea told the United States that it has shut down its nuclear reactor, the US State Department said on Saturday. The announcement came hours after a South Korean oil shipment entered a North Korean port—a promised reward for the reactor shutdown pledge.

If confirmed by a UN inspection team headed to the Yongbyon reactor, the shutdown would be the North’s first step in nearly five years toward de-nuclearisation.

“We welcome this development and look forward to the verification and monitoring of this shutdown by the International Atomic Energy Agency team,” State Department spokesperson Sean McCormack said in a statement.

After tortuous negotiations and delays—during which the North argued its nuclear programme was for self-defence—the reclusive regime said earlier this month that once it received the oil shipment, it would consider halting its reactor.

The 10-member team from the International Atomic Energy Agency arrived in the North Korean capital on Saturday afternoon. Team chief Adel Tolba said they would stay in North Korea as long as needed to complete its work at the Yongbyon plutonium-producing reactor, about 120 kms north-east of Pyongyang.