South Korea and Japan held rare high-level talks Wednesday on the sensitive issue of wartime sex slavery, which has contributed to a virtual freeze of diplomatic ties.

Japan's Kyodo News cited an unnamed government official as saying the Japanese side would indicate Tokyo is mulling an official apology and money for the so-called "comfort women" forced to work in military brothels.

The meeting was between Junichi Ihara, head of the Japanese foreign ministry's Asia and Oceania affairs bureau, and Lee Sang-Deok, South Korea's director-general for Northeast Asian Affairs.

Seoul said the talks were the first time high-level officials had met to discuss the "comfort women" issue in isolation.

Relations between Tokyo and Seoul are at their lowest ebb in years, mired in emotive disputes linked to Japan's 1910-45 colonial rule.

As US President Barack Obama heads to both Japan and South Korea next week, there is renewed impetus for its two allies to heal their fractured relationship, despite domestic pressures on both sides not to bend.

Japan has long maintained that all issues relating to the colonial period were settled under a 1965 bilateral treaty that normalized diplomatic ties with South Korea.

According to an official cited by Kyodo News, to offer another apology and further compensation would be formalized only after confirming the issue "has been completely settled," so that South Korea never brings it up again.

Fifty-five surviving former "comfort women" still live in South Korea.