U.S. Defense Secretary Chuck Hagel on Saturday urged Japan to improve relations with its neighbors after Prime Minister Shinzo Abe's visit to war-linked Yasukuni Shrine in Tokyo in late December fueled anger in China and South Korea.

"Secretary Hagel underscored the importance of Japan taking steps to improve relations with its neighbors," Defense Department press secretary Rear Adm. John Kirby said in a statement summarizing telephone talks between Hagel and Defense Minister Itsunori Onodera.

Abe's visit to Yasukuni Shrine on Dec. 26 angered China and South Korea, both of which suffered from Japanese wartime aggression, further worsening Japan's strained ties with the two countries.

The U.S. government has said it was "disappointed" to see Abe go ahead with the trip to Yasukuni because it would exacerbate tensions with China and South Korea.

Onodera tried to placate the U.S. government's anger over the shrine visit, telling Hagel that the prime minister reiterated the pledge that Japan must never wage war again, Japanese officials said.

On Jan. 1, Internal Affairs and Communications Minister Yoshitaka Shindo also visited the shrine, which honors Japanese leaders convicted as war criminals by an Allied tribunal along with millions of war dead.

On bilateral relations, Hagel expressed appreciation for the Japanese government's efforts in securing approval from the governor of Okinawa Prefecture for landfill work for the relocation of a U.S. Marine Corps air base within the prefecture, Kirby said.

Okinawa Gov. Hirokazu Nakaima approved on Dec. 27 the central government's request for the landfill permit to build a relocation facility for the Futenma air station off the Henoko coastal area of the city of Nago.

Kirby said the new facility is "a critical part of the realignment of U.S. forces on Okinawa."