Japan's chief delegate to the six-party talks on denuclearizing North Korea will visit Beijing on Friday, the Foreign Ministry said.

Akitaka Saiki, director general of the Foreign Ministry's Asian and Oceanian Affairs Bureau, is scheduled to meet with U.S. and South Korean counterparts Christopher Hill and Kim Sook during his two-day stay in China.

The delegates are scheduled to "exchange views on future process of the six-party talks," the ministry said.

The ministry also announced that Saiki is working with the Chinese government to address North Korean and bilateral issues during the stay. Pyongyang's denuclearization process, as well as bilateral progress on reinvestigating the abduction of Japanese citizens by North Korea, have recently stalled.

By restoring reactors at Yongbyon, Pyongyang is reportedly breaching a six-party pledge to disable its nuclear facilities, and no progress has been made on its promise to Japan to set up a domestic investigative commission and reopen probes into what happened to the Japanese abductees.

"The six-party talks are seeing a very difficult, wearisome phase," Senior Vice Foreign Minister Shintaro Ito told a news conference Thursday.

Saiki will be in China to "make progress on the issue and discuss how to restart North Korea's denuclearization process."

Japan has been informed by other countries that some of the North's equipment has been brought out of storage in Yongbyon, one of North Korea's key nuclear facilities.

"This is a matter of heavy concern," Ito said.