The breakthrough deal between South Korea and Japan on resolving the issue of Japan's wartime sexual slavery was made possible thanks to "leadership," "courage" and "statesmanship" of the leaders of the two countries, U.S. experts said Monday.

The experts also said that the agreement paves the way for greater trilateral security cooperation with the U.S. to deal with a rising China and a nuclear North Korea. What's important now is for Seoul and Tokyo to fight back nationalist pressure and sincerely carry out the agreement, they said.

"The agreement between Seoul and Tokyo to finally resolve the issue of World War II-era sexual slavery or 'comfort women' is tremendously important, even historic," said Evans Revere, a former U.S. diplomat and senior adviser for the Albright Stonebridge Group.

Earlier in the day, South Korean Foreign Minister Yun Byung-se and his Japanese counterpart, Fumio Kishida, reached the agreement in Seoul, under which Japan will admit responsibility for the wartime crime and pay reparations to the victims.

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.

"At that meeting, and for the first time, the two leaders committed themselves and their governments to a speedy resolution of this thorny issue. In doing so, they each created a personal stake in a favorable outcome -- something that was essential to the compromises that made this breakthrough possible," Revere said.

"Without their leadership, this agreement would not have happened."

The White House also praised the leaders of the two countries for "having the courage and vision to forge a lasting settlement to this difficult issue." National Security Advisor Susan Rice also said the U.S. looks forward to advancing trilateral security cooperation.

Under the agreement, 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 ($8.3 million) 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.

Bruce Klingner, a senior Korea expert at the Heritage Foundation, also called the deal "a stunning success achieved through diplomatic perseverance as well as the courage by Prime Minister Abe and President Park to overcome seemingly insurmountable differences."

But he said the two countries should fight back nationalist pressure if the deal is to come to fruition.

"Japanese ultra-right groups -- who deny Japanese imperial army involvement in wartime atrocities -- may seek to undermine support for the agreement. Korean non-government groups may argue the agreement doesn't go far enough in requiring Japanese contrition and demand additional Japanese concessions," Klingner said.

The expert also said that the agreement allows Seoul and Tokyo to "refocus attention from past differences to jointly focus on current security threats from North Korea and China" and paves the way for greater trilateral security cooperation with the U.S.

"Hopefully, South Korea will now be open to resurrecting an aborted 2012 military intelligence sharing agreement with Japan as well as integrating its national ballistic missile defense system into the more comprehensive and effective allied system," he said.

Scott Snyder, a senior expert at the Council on Foreign Relations, also praised Park and Abe.

"The agreement is a welcome step forward that should enable greater bilateral cooperation and trilateral cooperation with the United States. I believe it is good for both Korea and Japan and shows pragmatism and statesmanship on the part of both leaders," he said.

Victor Cha, chief Korea expert at the Center for Strategic and International Studies, said that the agreement "goes farther than most thought Japan would go in terms of admitting government responsibility," even though civic groups in South Korea may not be content.

"This should pave the way, hopefully, for a normalization of political relations for the remainder of the Park and Abe terms, including enhanced trilateral cooperation with the United States on regional security issues including military information sharing agreements among the allies," he said.

David Straub, a former State Department director for Korea and currently associate director for the Korean Studies Program at Stanford University, praised Park and Yun for "their determination, skill, and courage in getting the best possible terms from a conservative Japanese government."

"I believe that this agreement fully vindicates the 'comfort women,' and, because Prime Minister Abe agreed to it, it makes it virtually certain that future Japanese governments as well, whether conservative or progressive, will uphold the position and the agreement," he said.

"The agreement should result in the creation of a new, virtuous cycle in Korea-Japan relations. In future, both countries should be able to consider other issues in bilateral relations based on the merits of each issue, rather than having everything poisoned by a single issue," he added.

Dennis Halpin, a researcher at the Johns Hopkins University's U.S.-Korea Institute, said that the agreement would allow Abe to project an image as statesman and supporter of women's rights on the world stage and to "pursue Tokyo's long-standing elusive dream of a permanent U.N. Security Council seat."

It would also be good for the U.S. as the two key allies are now able to work together to support President Barack Obama's "pivot to Asia" and deal with the challenges of a nuclear North Korea and a rising China, the expert said.

But South Korea could face tensions with nongovernmental groups if it tries to move the statue of a girl symbolizing sexual slavery victims set up in front of the Japanese Embassy in Seoul, Halpin said, pointing out that the statue has become something of Korea's own Statue of Liberty.(Yonhap)