UN Chief Ban Ki-moon has called out Japanese Prime Minister Shinzo Abe's administration, suggesting his government needs to do more to foster better ties with both China and South Korea.

Delivering a speech in Tokyo to commemorate the 70th anniversary of the establishment of the United Nations, Ban Ki-moon says the UN has been pushing for regional cooperation in different parts of the world, but says northeast Asia remains "a missing link."

Speaking after the UN chief, Shinzo Abe did not respond to Ban Ki-moon's suggestion, but did say Japan is "built on deep regret over the past war."

Japanese political observer Morita Minoru suggests Abe's comments don't go far enough.

"Japan has an unshakable responsibility for World War II. Therefore, to realize peace has become Japan's current biggest responsibility. If we neglect this basic point and fail to maintain the peaceful relations with our neighboring countries, then whatever Japan does is meaningless. I believe what Abe is doing is totally wrong."

Japan's relationship with China and South Korea has been strained in recent years amid disputes over both historical and territorial issues.

Political observers in Japan expect Shinzo Abe may move to water-down previous admissions of Japanese wrong-doing as part of a speech later this year marking the 70th anniversary of World War II.