The official said Thursday the Foreign Affairs Ministry was prepared an official letter to urge Japan to enter negotiations to discuss whether reparations were still due for its sexual enslavement of South Koreans more than 50 years ago, Yonhap reported.
Historians say up to 200,000 women, including many Koreans, were forced to work in front-line brothels for the Japanese army during the war when the Korean Peninsula was under Japanese rule.
"We are considering various ways, including whether to actually send the letter" to try to resolve the issue, the official said.
The ministry sent two similar letters to Japan in 2011 to try to use diplomatic channels to help the former "comfort women" receive their demanded compensation and an official apology, Yonhap said. Neither letter was answered.
"The ministry is very regretful about Japan showing no response to South Korea's such calls," ministry spokeswoman Han Hye-jin said. "We urge again Japan to come up with a speedy response."
Han said 56 former sex slaves, mostly in their 80s, were still alive.
The ministry will determine when to send the letter after examining developments in Seoul-Tokyo relations, she said.
Japan has denied liability, claiming a 1965 treaty between the two countries cleared it of further responsibility. Under the treaty, the countries established diplomatic ties and agreed to absolve Japan of wrongdoings against South Koreans who suffered and were enslaved under Japan's colonial rule from 1910 through 1945.
In 2011, South Korea's Constitutional Court ruled the Foreign Ministry's inaction in dealing with the issue of compensating the former sex slaves was unconstitutional and infringed upon the victims' rights.