The chief U.S. nuclear envoy to North Korea was traveling to the communist country Thursday ahead of the expected resumption of talks on halting Pyongyang's nuclear weapons program, the Japanese government said.

"We are aware that Hill will visit North Korea starting today," Chief Cabinet Secretary Yasuhisa Shiozaki told reporters in Tokyo. Shiozaki declined to provide any other details.

South Korea's Yonhap news agency quoted an unnamed source as saying that North Korea invited Christopher Hill to visit, adding that the envoy was to meet North Korean Vice Foreign Minister Kim Kye-gwan for talks on denuclearization and normalization of the North-U.S. relations.

Hill was staying at the U.S. Osan Airbase in South Korea and planned to fly to the North on a military plane, Yonhap said. Hill planned come back to Seoul on Friday, it said.

Japan's NTV televison reported that Hill was already in the North.