A group of South Korean women who were forced into sex slavery by Japan during World War II in order to serve its soldiers announced on Tuesday that they will sue the Japanese government for $20 million in a California district court on July 1 unless it makes suitable amends before then.

The 10 women will seek $2 million each in compensation for what they have called systemic war crimes committed against them by soldiers and Japanese companies under the direction of the Japanese government, according to the South Korean news agency Yonhap.

The matter has long created a wedge in South Korean-Japanese relations, and has resurfaced again as the two countries mark the 50-year-anniversary of diplomatic ties and the 70th anniversary of the end of World War II this year.

Since all legal avenues for reparations have previously failed in South Korea and Japan, the women plan to pursue their case in a US court, targeting companies including Mitsubishi and others involved in the alleged war crimes, AFP reported. Businessmen also reportedly used military brothels — euphemistically known as "comfort women stations" — during the time they were active, and semi-governmental or independent companies were allegedly involved in operating the operations in occupied territories.

Twelve women were originally involved in the lawsuit, but two have since died. All of the women are over 80 years of age. It is estimated that the Imperial Japanese army forced some 200,000 women — mostly Korean, but also Chinese, Filipino, Malaysian, Indonesian, and other Asian women — into sexual slavery, many of whom were abducted from their homes and sent overseas to work in the brothels.

"The Japanese government should offer an official and sincere apology for wrongdoings by their ancestors and restore our honor," one of the women, 89-year-old Kim Bok-Dong, told reporters outside the Japanese Embassy in Seoul.

Lee Yong-soo, a former South Korean sex slave for Japan's World War II soldiers, touches a statue dedicated to the victims of Japan's wartime sex slavery as she visits a public library's park in Glendale, California, on May 6, 2015. The statue of a young girl is a replica of one set up in front of the Japanese Embassy in Seoul. (Photo via EPA/Yonhap)

If the government fails to do so, the group will lodge the suit under international law in California on July 1, the women's attorney Kim Hyung-Jin said. Comfort women brought a similar class-action lawsuit before a Washington, DC-based federal court in 2000, but the court said the case was outside its jurisdiction and sided with Japan.

"Money is absolutely not the point," Kim insisted. "The point is that Japan admits to its war crimes and offers a sincere apology."

Japanese authorities contend the issue was settled after the government delivered a package of aid and loans worth $800 million to South Korea under a normalization agreement in 1965, under which Japan says South Korea renounced rights to reparation and property claims.

Japan's Chief Cabinet Secretary Yohei Kono also issued a statement in 1993, known as the Kono Statement, in which, after years of denials, he acknowledged that the government had coerced women to work in brothels.

"The then Japanese military was, directly or indirectly, involved in the establishment and management of the comfort stations," he said, noting that "the recruitment of the comfort women was conducted mainly by private recruiters who acted in response to the request of the military."

An apology by Prime Minister Tomiichi Murayama followed in 1994 for any suffering caused by the Japanese military.

"On the issue of wartime 'comfort women,' which seriously stained the honor and dignity of many women, I would like to take this opportunity once again to express my profound and sincere remorse and apologies," Murayama said. "I believe that one way of demonstrating such feelings of apologies and remorse is to work to further promote mutual understanding with the countries and areas concerned as well as to face squarely to the past and ensure that it is rightly conveyed to future generations."

But some conservative lawmakers and nationalists in Japan continue to deny the government's involvement in setting up and running the army brothels and have sought to review or retract the Kono Statement. They assert that the women were prostitutes who willingly worked in the sex trade.

A South Korean supporter of former "comfort women" holds a banner during a rally against the Japanese government held in front of the Japanese Embassy in Seoul, South Korea, on April 29, 2015. (Photo by Jeon Heon-kyun/EPA)

South Korea maintains that Japan has not done enough to atone for the atrocities. Last Friday, state representatives did not show up at the first conciliation hearing between Japan and the comfort women in Seoul, Yonhap reported. During his first term in government, Japanese Prime Minister Shinzo Abe suffered some international backlash after he said he didn't believe the women were forced into sexual slavery by the military.

"The fact is, there is no evidence to prove there was coercion,'' he said at the time.

During a visit to the US in April, Abe was asked whether he would apologize for the system of forced prostitution.

"I am deeply pained to think about the comfort women who experienced immeasurable pain and suffering as a result of victimization due to human trafficking," he said. "This is a feeling that I share equally with my predecessors."

Abe's avoidance of an apology prompted a group of 187 historians and scholars to sign an open letter calling for his government to "show leadership by addressing Japan's history of colonial rule and wartime aggression in both words and action" on the 70th anniversary of World War II's end.

"The outsourcing of the apology and acknowledgment to former politicians lacks empathy and sincerity," Jeff Kingston, a signatory and professor of history at Temple University Japan, told the Financial Times.

Last week, a spokeswoman for Japan's Liberal Democratic Party (LDP) announced that Abe supported the Kono Statement and would likely address the issue of forced prostitution and its violation of human rights in his planned speech to mark the anniversary of the war's conclusion.