He told a parliamentary panel on Thursday that wartime leaders, including his cabinet minister grandfather Nobusuke Kishi, had "great responsibility" for starting the war.
Kishi was imprisoned as a war criminal but was never tried and went on to serve as prime minister from 1957 to 1960.
"As a result of starting war, many Japanese lost their lives and families and we left many scars on the people of Asia," said Abe, at 52, Japan's first premier born after World War Two.
"Particularly, those people in the position of leader at the time, including my grandfather, had great responsibility."
Abe also referred in parliament this week to a historic 1995 statement by then-prime minister Tomiichi Murayama apologizing for the suffering Japan caused in Asia during the war.
In a nod to an issue highly emotive in South Korea, Abe said he accepted as valid a 1993 Japanese government statement admitting the Imperial Japanese Army forced thousands of mostly Asian women, many of them Korean, to provide sex for soldiers. By Linda Sieg Fri Oct 6, 9:19 AM ET Reuters
During a House of Representatives Budget Committee session, Abe said he accepts a statement given in 1995 by then Prime Minister Tomiichi Murayama in which he apologized and expressed remorse for Japanese aggression and the suffering inflicted on countries under its colonial rule before and during World War II.
Abe also said he accepted a statement issued in 1993 by then Chief Cabinet Secretary Yohei Kono in which the government officially acknowledged that the Imperial Japanese Army forced Asian women to provide sexual services for soldiers as "comfort women."
As for his grandfather, the late former Prime Minister Nobusuke Kishi, Abe gave his views on Kishi's role in the conflict.
"As a result of starting the war, many Japanese lost their lives and families, and we left many scars on the people of Asia," Abe said. "Those in leadership positions, including my grandfather, were held responsible. The decision [to start war] might therefore have been wrong."
Kishi, the commerce and industry minister when Japan declared war against the United States and Britain in 1941, was detained as a Class-A war criminal suspect after World War II, but was not indicted. He was released soon after Tojo and six others were hanged in 1948 and went on to serve as prime minister from 1957 to 1960.
At the lower house Budget Committee on Friday, Abe said, "Former Foreign Minister Mamoru Shigemitsu [a Class-A war criminal] was later awarded the Grand Cordon of the Order. If he was a war criminal, that could never happen. As for Article 11 of the San Francisco Peace Treaty, we did not promise that we would treat them [Class-A war criminals] as criminals.The Yomiuri Shimbun(Oct. 7, 2006)
It seems Abe is a practical politician, but I think he should be clearer on the A criminals.
You can say Tokyo tribunal had unfair aspects, but Japan accepted its judgment.
Then A-criminals are A criminals, internationally and domestically.