Prime Minister Junichiro Koizumi has vowed that Japan would never go to war again as he prayed at a World War II memorial on a tiny Pacific island.
Mr Koizumi said Japan would never forget the war lessons
He was the first Japanese premier to attend a service in Iwo Jima, where nearly 7,000 US Marines and some 21,000 Japanese defenders died in March 1945.
The trip comes as Japan's ties with China have been chilled by Mr Koizumi's annual visits to the Yasukuni shrine.
China sees the shrine in central Tokyo as a symbol of Japan's past militarism.
The shrine honours Japanese war dead along with war criminals.
The issue is also expected to figure prominently when Mr Koizumi meets South Korean President Roh Moo-hyun on Monday.
"Our country has never taken part or been involved in war after the end of the [World ] war and has maintained peace," Mr Koizumi said during the memorial service in Iwo Jima.
The Iwo Jima memorial in Virginia commemorates the battle
"We will never let the lessons from the war fade away," he said.
Mr Koizumi was speaking in front of a cenotaph built in 1971 to commemorate those who died in the fierce battle that lasted 36 days.
The fighting has been immortalised by a photograph of American soldiers raising the Stars and Stripes flag on Mount Suribachi.
The volcanic island lays about 1,250km (780 miles) south of Tokyo.