Prime Minister Shinzo Abe said July 31 that a U.S. resolution demanding Japan's formal apology over its practice of forcing thousands of Asian women into sex slavery during World War II was regrettable because Japan has made amends.

The U.S. House of Representatives on July 30 approved a resolution urging Japan to "formally acknowledge, apologize and accept historical responsibility in a clear and unequivocal manner" for the suffering of so-called "comfort women."

"The resolution is regrettable," Abe told the media.

"I explained my views and the government's response on this matter during my visit to the United States in April."

Historians say the Imperial Japanese Army forcibly sent hundreds of thousands of women, mainly from Korea, China and the Philippines, to wartime Japanese military brothels to work as prostitutes in the 1930s and 1940s.

Since the government's acknowledgment in the early 1990s, Japanese leaders, including Abe, have repeatedly apologized.

Abe, however, indicated that he would formally apologize.

"The 20th century was a period when violations of human rights occurred.

"It is important to make the 21st century a brighter period for people worldwide," Abe said.

Chief Cabinet Secretary Yasuhisa Shiozaki said Japan had no plans to lodge a protest with Washington over the resolution.

"We have worked to clearly explain Japan's view," Shiozaki said. "We will continue to do so."