With his support rate in media polls riding high thanks to his economic policies, Prime Minister Shinzo Abe may finally be revealing shades of his true colors as a right-leaning historical revisionist four months into his administration.

The latest controversy swirls around whether he is upholding a key government-issued apology for Japan’s war responsibility. His rhetorical maneuvering has caused a big stir in South Korea and is reportedly raising worries in the U.S. government as well.

Abe had been considered upholding the 1995 statement issued by Prime Minister Tomiichi Murayama, as he straightforwardly acknowledged in previous Diet sessions that Japan “caused tremendous damage and suffering to the people of many countries,” as stated in the unequivocal Murayama statement.

But earlier this week, Abe started backtracking. During an Upper House session Monday, he said he is “not upholding all of (the statement) as it is.”

“Speaking of the Murayama statement, I talked about some parts that I can empathize with,” Abe said, indicating there may be some parts he does not agree with.

On Tuesday in the Upper House, Abe then claimed that the definition of “aggression” in general has yet to be “firmly determined” by academics or the international community.

What is described as aggression “can be viewed differently” depending on which side you are on, Abe said.

He didn’t elaborate, but conservative nationalists have argued that Japan’s wars in the 1930s and ’40s were waged in self-defense, not aggression.

The South Korean media slammed Abe’s comment and said that he is denying Japan fought a war of aggression.

According to a Kyodo News report, Washington has conveyed its concern to Tokyo through an unofficial diplomatic channel, saying Abe’s stance on history issues could adversely affect Japan’s relationships with its neighbors.

The Murayama statement has been upheld by every Cabinet since it was made, including Abe’s first team from 2006 to 2007, and is widely regarded as Japan’s key apology for its wars of aggression and colonial rule in Asia.

Asked to comment, Chief Cabinet Secretary Yoshihide Suga on Friday quoted some key parts of the Murayama statement and repeated the apology for the “tremendous damage and suffering” Japan caused.

But he declined to comment on other parts of the statement, including whether Japan fought a war of aggression.

“The Japanese government has regarded those history issues in a spirit of humility, expressing our feelings of deep remorse and our heartfelt apology,” Suga said.

“The view of the Abe Cabinet is exactly the same,” he added.

Suga then insisted that he will not discuss war-related issues further, saying the Murayama statement was issued to mark the 50th anniversary of the end of World War II, followed by a similar statement by Prime Minister Junichiro Koizumi to mark the 60th anniversary in 2005.

“We’d like to issue a new statement to mark the 70th anniversary” in 2015, Suga said.