Prime Minister Shinzo Abe on Wednesday expressed "deep remorse" over Japan's actions toward neighboring Asian nations during World War II, but stopped short of a full apology for mass sexual slavery.

"Post war, we started out on our path bearing in mind feelings of deep remorse over the war," Abe said in a historic address to a joint meeting of the US Congress.

"Our actions brought suffering to the peoples in Asian countries. We must not avert our eyes from that."