Japanese Prime Minister Shinzo Abe must include a clear apology for the country's sexual enslavement of women during World War II in an address he is expected to deliver at a joint meeting of the U.S. Congress, an American congressman said Wednesday.

Abe has sought a congressional invitation to address a joint session of the House and the Senate when he visits Washington next month. Indications have grown he would get the chance despite objections that the nationalist leader is not qualified for the honor.

Opponents have accused Abe of attempting to whitewash Japan's militaristic past and wartime atrocities, especially the country's sexual enslavement of women for its troops during World War II, and is still refusing to clearly apologize for the crime.

Abe would be the first Japanese leader to address a joint meeting of Congress.

"I would hope that Prime Minister Abe would make sure that ...he acknowledges the systematic kidnapping of girls and women during the 1930s and 1940s during the second world war, that they were responsible for, that he apologizes on behalf of the government, that the apology be unambiguous, and that he accepts the historical responsibility," Rep. Mike Honda (D-CA) told reporters.

Should Abe want to become a leader in women's rights, as he said in a speech at the U.N. General Assembly last year, he must apologize to the victims of sexual slavery, Honda said, adding that "nothing less than" a clear apology is enough for him to be a global leader.

"Their government needs to apologize for the past, be responsible for the present, and provide the leadership of the future. In order to do that you have to unequivocally apologize and accept the historical responsibility of what happened through the systematic kidnapping of girls through the Japanese Imperial military," the lawmaker said.

Honda, who has long championed the rights of sexual slavery victims, said it is still unclear whether congressional leaders had invited Abe, but he got a sense that they have.

"When these kinds of things happen, they try to keep a very high security level so that they don't share a lot of information beforehand. This is not unusual," he said.

The Washington-based newsletter "Nelson Report" also said that House Speaker John Boehner has agreed to officially extend an invitation to Abe for a speech to a joint meeting of Congress before Congress adjourns on April 29 for the spring recess.

The report said, however, that no official announcement of the invitation will be made pending completion of certain technicalities and discussions, including "final sign-off" from House Foreign Affairs Committee Chairman Ed Royce (R-CA).

Royce's office rejected the report, saying such a decision is totally up to the speaker.

"Reports of the chairman's 'sign off' are inaccurate. The decision on these types of invitations lies solely with the speaker, not with the chairman of the Foreign Affairs Committee," the official told Yonhap News Agency without providing any further details.

Boehner's office said it does not have "any news to announce at this point."

Korean-American organizations have campaigned against such an address by Abe and collected about 6,000 signatures so far. They also ran a full-page advertisement in the newspaper Hill demanding Abe apologize for the sexual slavery issue before speaking before Congress.

Those opposed to an Abe speech have been looking to Royce to raise objections, just as former committee chairman Henry Hyde derailed Japanese Prime Minister Junichiro Koizumi's push for an address in 2000, citing his visits to a Tokyo shrine honoring war dead, including war criminal.

Abe's visit, expected to begin around April 26, is likely to be an occasion for the U.S. and Japan to celebrate progress in negotiations on an Asia-Pacific free trade deal, known as the Trans Pacific Partnership (TPP), and a revision to their defense guidelines.

White House officials have repeatedly said they would welcome Abe with grand ceremonies and other elaborate protocols as is with a state visit, even though Abe's trip is technically an official visit as he is not a head of state. (Yonhap)