Top U.S. nuclear envoy Christopher Hill has urged North Korea to take steps to verify its nuclear declaration.

Hill said Saturday that Washington will be prepared to immediately delist Pyongyang from the U.S. terrorism blacklist once the North agrees on rules allowing inspectors to verify its declaration of its nuclear program and materials.

He made the statement to reporters after talks with Chinese counterpart Wu Dawei in Beijing.

On reports that Pyongyang is rebuilding its main Yongbyon reactor, Hill said reconstituting Yongbyon is not an easy piece of work and will likely take more than a year. He added the North’s recent moves apparently demonstrate the communist state’s fears over nuclear verification.