U.S. lawmakers urged Japanese Prime Minister Shinzo Abe on Tuesday to offer a sincere apology for the country's wartime sexual enslavement of women as two surviving victims sued Tokyo for damages for insulting them as prostitutes.

The victims, both in their 90s, filed the suit with a federal court in San Francisco, demanding $20 million in damages each.

Named as defendants were the Japanese government, the late Japanese Emperor Hirohito, former Japanese Prime Minister Nobusuke Kishi and seven Japanese companies, including Mitsui and Mitsubishi.

"The Japanese government is practically insulting those victims by calling them voluntary prostitutes. It is like calling the prisoners in Auschwitz as 'voluntary workers,'" said Kim Hyung-jin, a lawyer for the victims, during a news conference in Washington.

In Congress, lawmakers stepped up calls for Japan to apologize for the atrocity as they marked the eighth anniversary of a landmark 2007 House of Representatives resolution urging Japan to fully acknowledge and take full responsibility for the issue.

In particular, Rep. Mike Honda, who wrote the 2007 resolution, urged Japan to learn from Germany, which even enacted a law that makes it a crime to deny wartime historical facts.

"Prime Minister Abe has the historic opportunity to take leadership and doing something and saying, 'You are right. We were wrong. We apologize. We will pass a law that will say we apologize, we accept historical responsibility. We will pass a law that says our textbooks will teach our youngsters what happened in the past so they won't happen in the future,'" Honda said during an event marking the resolution's anniversary.

"We know that German Chancellor (Angela) Merkel has told Abe when Abe visited Germany, 'You know, we faced our past and we made our apologies. In fact, I think we even have a law in Germany that if you say that, the death camps did not exist, you would be fined for a violation of a law there. That's how serious they were," he said.

Those attendinng the event included Lee Yong-soo, one of the suriving victims.

Honda, who has long been at the forefront of efforts to get Japan to admit and apologize for the sexual slavery, wrote the landmark resolution (H.R.121) and helped it pass through the House unanimously. The resolution urged Japan to acknowledge its actions, apologize and accept historical responsibility in a clear and unequivocal manner.

In April, Abe failed to apologize when he made a visit to the U.S. that included an address at a joint session of Congress. Abe's upcoming statement, expected to be issued next month to mark the 70th anniversary of the end of World War II, will be watched closely, though chances of an apology appear low.

Historians estimate that up to 200,000 women, mainly from Korea, which was a Japanese colony from 1910 to 1945, were forced to work in front-line brothels for Japanese soldiers during World War II. But Japan has long attempted to water down the atrocity.

Such efforts have intensified after Abe came to power.

Abe's cabinet, for example, angered South Korea last year with its attempt to "review" a 1993 statement of apology, known as Kono Statement. Though Japan later said it still stands by the apology, the move was seen as an attempt to undermine the apology's credibility.

His government also came under strong criticism last year after pressuring an American publisher to revise a description of the sexual slavery issue in a school history textbook in an apparent attempt to water down the atrocity.

"Prime Minister Abe has been hearing from scholars, saying, 'It did happen, prime minister. Don't change the history books of other countries,'" Honda said. "Prime Minister Abe has to learn that to be a good leader in a democratic country, you have to accept historical responsibility. You have to do the hard things."

The congressmen also stressed that time is running short for the surviving victims.

"We only have 49 halmonies (grandmothers) that are at the House of Sharing in Korea and there are others in other countries that are waiting for an apology from the government of Japan. The government of Japan through Abe owes an apology to return to the

200,000 comfort women their dignity, their spirit," he said.

Reps. Bill Pascrell, Adam Schiff and Judy Chu made similar appeals.

"We are so disappointed with the Japanese government report released last year on the Kono Statement, stepping back from taking full responsibility for the immeasurable pain and incurable wounds suffered by the comfort women," Pascrell said.

"No one should ever be subjected to human rights abuses they faced. As a member of the congressional human rights caucus, I will continue to work every day to ensure our children and our children's children can inherit a world where these types of atrocities are a thing of the past," he said.

Schiff said such a "dark chapter" of history won't be closed and healed until there is a full and forthright acknowledgment of responsibility by Japan, while Chu said Japan's sexual enslavement is the "largest case of human trafficking in the 20th century and there needs to be an apology." (Yonhap)