Officials say Japan has asked South Korea's government to stop a group of elderly former sex slaves from erecting a monument near the Japanese embassy in Seoul.

The women were forced into prostitution serving Japanese soldiers during World War II. For years, they have protested in front of the Japanese embassy every Wednesday, seeking an apology and compensation. They plan to erect the memorial stone when they hold their 1,000th demonstration in December.

Japan's Kyodo news agency quotes a foreign ministry official saying South Korea has been told the memorial could negatively affect relations between the countries. The official says Seoul has been asked to deal with the matter “in an appropriate manner.”

South Korea's Yonhap news agency quotes officials in that country confirming the request. But the officials say the monument does not require government approval and would be difficult to block.

The demands of the sex slaves, who were called “comfort women,” have been a longstanding source of tension between the countries. South Korea's Constitutional Court ruled last month that the government is obliged to pursue a settlement with Japan.

Tokyo maintains the issue was settled in a 1965 normalization treaty in which Japan provided South Korea with $800 million in grants and soft loans.