The United States on Monday praised South Korea and Japan for reaching a breakthrough deal on resolving the issue of Japan's wartime sexual slavery that has seriously plagued relations between the two key American allies for years.

South Korean Foreign Minister Yun Byung-se and his Japanese counterpart, Fumio Kishida, reached the agreement in talks in Seoul earlier in the day, which centers on Japan's admission of responsibility for the wartime crime and plans to pay reparations to the victims.

The deal removes the biggest thorn in relations between Seoul and Tokyo, and offers hope not only for greater cooperation between the two neighbors, but also for significant progress in U.S. efforts to forge stronger security cooperation with the two allies in a region marked by a rising China.

"The United States congratulates the governments of Japan and the Republic of Korea on reaching an agreement, which they have made clear 'finally and irreversibly' addresses the tragic treatment of 'comfort women' during World War II," U.S. National Security Advisor Susan Rice said.

The U.S. supports the agreement and its full implementation, and believes "this comprehensive resolution is an important gesture of healing and reconciliation that should be welcomed by the international community," Rice said in a statement.

"The United States applauds the leaders of the ROK and Japan, two of our most important allies, for having the courage and vision to forge a lasting settlement to this difficult issue," she said.

"We look forward to deepening our work with both nations on a wide range of regional and global issues, on the basis of mutual interests and shared values, as well as to advancing trilateral security cooperation," she added.

Secretary of State John Kerry issued a similar statement, saying the agreement will "promote healing and help to improve relations" between two of the most important U.S. allies. He also praised the leaders of the two countries and called for the international community to support the agreement.

"We look forward to continuing to work with both countries on regional and global issues, including advancing our economic ties and security cooperation," he said.

State Department deputy spokesman Mark Toner said he is aware that some Korean victims still feel aggrieved even with Monday's agreement, but it is for South Korea's government to work with them to address their concerns.

The spokesman also said that it's incumbent upon the government of Japan to "sell this agreement or to convince Japanese people that this agreement is in the best interest of Japan."

"This agreement will not necessarily answer or appease everyone's concerns going forward, but that said, we do support this agreement as a way forward to heal this wound," he said at a regular press briefing.

A senior State Department official told reporters in a conference call that Monday's agreement will open a new chapter in cooperation between Seoul and Tokyo and is as important as the Trans Pacific Partnership free trade deal.

"A region in which Japan and Korea are trading, are collaborating, are working together, are exchanging goods and services, ideas, culture, tourists, scientists, et cetera, without reservation, without hindrance, is going to be a more stable, secure and prosperous Asia," the official said.

Under Monday's deal, Japan formally acknowledged its responsibility for forcing Korean women into sexual servitude for its troops during World War II and agreed to offer 1 billion yen in reparations to the victims through a fund to be created by the South Korean government.

South Korea promised to end the dispute once and for all if Japan fulfills its responsibilities.

The deal came after President Park Geun-hye and Japanese Prime Minister Shinzo Abe held their first-ever one-on-one summit in early November and agreed to accelerate negotiations on the issue in a year marking the 50th anniversary of the establishment of bilateral diplomatic relations.

Historians estimate that more than 200,000 women, mostly Koreans, were forced to work in front-line brothels for Japanese soldiers during the war. Korea was under Japanese colonial rule from 1910 to 1945. The victims are euphemistically called "comfort women."

South Korea demanded Japan offer a formal apology and proper compensation to the victims before they all die. Earlier this month, a former South Korean comfort woman died at age 96, reducing the number of surviving victims in the country to 46.

Japan claimed it fulfilled its legal responsibility in a package deal under the normalization treaty of 1965, but South Korea insisted the comfort women issue should be handled separately as it constitutes a crime against humanity.

Frayed relations between the two allies have been a key cause for concern for the U.S. as it seeks to bolster three-way security cooperation seen as a key pillar for President Barack Obama's "pivot to Asia" initiative aimed in part at keeping a rising China in check. (Yonhap)