Japan got input from South Korea on the sensitive wording of a landmark apology in 1993 to women, many Korean, who worked in Japan's wartime military brothels, an expert panel said after reviewing evidence that led to the statement.
Chief Cabinet Secretary Yoshihida Suga, commenting on the report, repeated that Japan would not revise the statement on the "comfort women", as they are euphemistically known in Japan.
"It is still very painful to think of the sufferings that the women endured and there is no change in the government's stance on that," Suga told a news conference.
The topic of "comfort women" has long been a thorn in Japan's ties with South Korea, which says Japan as not sufficiently atoned for the women's suffering.
The 1993 "Kono Statement", named after then-Chief Cabinet Secretary Yohei Kono in whose name it was issued, acknowledged Japanese authorities' involvement in coercing the women to work in the brothels.
Many Japanese conservatives, however, say there is no proof of authorities' involvement - a stance adopted by Prime Minister Shinzo Abe's first 2006-2007 administration - and that other countries also sexually exploited women during wartime.
Abe has questioned the Kono Statement in the past and in what many saw as a nod to his conservative base, the government asked five experts to review it. But mindful of potential diplomatic fallout, Abe has also said he would not revise it.
Relations between Japan and South Korea have grown frosty in recent years, frayed by a territorial row over a disputed island and by the legacy of Japan's 1910-1945 colonization of the Korean peninsula.
On Friday, South Korea began a shooting drill in disputed waters off the islands, which are controlled by Seoul but also claimed by Tokyo. Japan protested the drill.
China reiterated its view that Japan should face up to its past history of invasion in Asia.
"There is irrefutable evidence for these crimes," Chinese Foreign Ministry spokewoman Hua Chunying told a news briefing.
"Any move which tries to overturn the crimes of history will be unpopular and cannot succeed."
Japan says the matter of compensation for the women forced to work in the brothels was settled under a 1965 treaty establishing diplomatic ties. In 1995, Japan set up a fund to make payments to the women from private contributions, but South Korea says that was not official and so not enough.
While Abe himself has said he was "deeply pained" by the women's suffering, conservative politicians repeatedly cast doubt on Japan's apologies by suggesting Japan has been unfairly singled out or that many of the women were not coerced.
"We have to look into what these documents were originally made from," said Hiroshi Yamada, of the conservative Japan Restoration Party, who originally called for the review.
"If not, then we will simply be told that it is Japan's viewpoint and that it's not what South Korea thinks. The same thing will just happen."
The review of the Kono Statement comes at a delicate time for Abe's security agenda, as he pushes to end a ban on sending Japan's military to aid a friendly country under attack - a major shift in defense policy likely to upset Seoul and Beijing.