The chief UN nuclear inspector expressed optimism for better relations with North Korea as he arrived Tuesday in Pyongyang for talks on implementing a landmark nuclear disarmament agreement that calls for the North to stop making plutonium for atomic bombs. "We hope we can make progress in our relationship," Mohamed ElBaradei, head of the Vienna-based International Atomic Energy Agency, said after arriving in Pyongyang, Associated Press Television News reported. "I hope the outcome will be positive." North Korea expelled IAEA inspectors after U.S. officials accused the communist nation in late 2002 of running a secret uranium enrichment program. The North then restarted its main reactor at Yongbyon and is believed to have produced enough plutonium in recent years for as many as a dozen nuclear bombs - including the weapon it detonated in an underground test blast on Oct. 9. Under an agreement last month with the US and four regional powers, North Korea has until April 14 to shut down and seal the Yongbyon nuclear reactor and a reprocessing facility in exchange for an initial shipment of aid. The IAEA is supposed to monitor and verify the shutdown.