Japan has no plan to revise a landmark 1993 apology over wartime sex slavery, the government's top spokesman said on Monday.

The announcement comes despite a controversial review of the statement in Japan that has sparked a backlash both at home and abroad.

The landmark apology, known as the Kono Statement, acknowledged official complicity in the coercion of women from across Asia into a system of wartime brothels, an issue that draws particular resentment in China and South Korea.

South Korean President Park Geun-hye has warned Japan that it would face "isolation" if it pushed ahead with a move to revisit the apology.

But Japanese Chief Cabinet Secretary Yoshihide Suga told reporters in Tokyo on Monday that "the government does not intend to revise the Kono Statement".

Japanese government has also come under fire from Asian neighbors for setting up a group to verify the accuracy of interviews more than 20 years ago with women who said they worked as sex slaves for Japanese soldiers before and during World War II.

Historians say tens of thousands of women served as sex slaves, euphemistically called "comfort women" in Japan. Some Japanese nationalists have long insisted that women in wartime brothels were voluntary prostitutes, not sex slaves.

In 1993, after hearing testimony from 16 Korean women, the Kono statement offered "sincere apologies and remorse" to the women and vowed to face the historical facts squarely.

The current review was aimed at verifying historical facts, Suga said.

"There have also been suggestions that Japan might have negotiated with South Korea over the content of the apology" at the time, he added.

It was unclear what would happen if Tokyo's review was at odds with the official apology.

Japan and South Korea will hold talks at vice-ministerial level this week, the Japanese Foreign Ministry said, in a move which local media said could help mend their strained ties and open the door to a meeting of top leaders.

Japanese Deputy Foreign Minister Akitaka Saiki will visit Seoul on Wednesday and Thursday to meet with his newly appointed South Korean counterpart, Cho Tae-yong, the ministry said.

Historians say up to 200,000 women, mostly from Korea but also from the Chinese mainland, Taiwan, the Philippines and the Dutch East Indies (present-day Indonesia) were forced to serve as sex slaves in Japanese army brothels.

But the conservative government of Prime Minister Shinzo Abe has repeatedly said evidence given by "comfort women" that forms the basis of the apology is to be re-examined.

Repeated wavering on the issue among senior right-wing politicians has contributed to a feeling in South Korea that Japan is in denial and is not sufficiently remorseful.

The move to revisit the statement has raised eyebrows not only in South Korea but also in the United States and among Japanese historians.

A senior official at the US embassy in Tokyo has expressed "strong concern" over Tokyo's plans, the Tokyo Broadcasting System reported on Monday.

An embassy press officer declined to comment on the report.

AFP - AP