South Korea will closely monitor Japanese Prime Minister Shinzo Abe's remarks throughout his trip to the United States next week, not just during his address to the U.S. Congress, a government official said Friday.

Much attention has been focused on what Abe will say in his address to a joint session of the Congress on Wednesday, with South Korea demanding a clear expression of apology over Japan's wartime atrocities.

South Korea, which suffered under Japanese colonial rule from 1910-45, has especially demanded an apology and compensation for the Korean women who were forced into sexual slavery for Japan's World War II soldiers.

"No one knows for sure what he will say," a South Korean government official with knowledge of the issue said on condition of anonymity. "Abe will probably adjust the words until the last minute."

Abe has said he feels no need to repeat the apologies of some of his predecessors. On Wednesday, he drew criticism from Seoul after he simply expressed "deep remorse" over Japan's aggressions during World War II.

The official stressed that South Korea will be following Abe's words throughout his week-long visit to the U.S. to gauge his position on Japan's wartime past.

Abe, who begins his trip Sunday, is scheduled to deliver a speech at Harvard University and also make stops in San Francisco and Los Angeles.

"It's possible that Abe will address (the historical issues) in his other speeches as he has to consider both his domestic audience at home and critical public opinion in the U.S.," the official said.

On Thursday, a bipartisan group of U.S. congressmen, including the House Foreign Affairs Committee chairman, called on Abe to address historical tensions with South Korea so as to bolster trilateral cooperation.

The 25 lawmakers, including Reps. Mike Honda (D-CA) and Ed Royce (R-CA), issued the appeal in a joint letter to Japanese Ambassador to Washington Kenichiro Sasae.

"We sincerely hope Prime Minister Abe's visit will lay the foundation for healing and humble reconciliation by addressing the historical issues," they said. (Yonhap)