President Park Geun-hye and Japanese Prime Minister Shinzo Abe agreed Monday to speed up negotiations to quickly resolve the issue of former South Korean sex slaves for Japan's World War II soldiers, Cheong Wa Dae said.

The agreement was reached at the first summit between the leaders of the two neighbors in more than three years.

"The two leaders agreed to speed up consultations to try to quickly resolve the issue of 'comfort women,'" the presidential office said, referring to the former sex slaves.

Park said the issue is the "biggest stumbling block" to bilateral relations.

The presidential office did not provide any specific time frame for a new round of talks on the former sex slaves.

Seoul and Tokyo recently held a ninth round of working-level talks on the issue, though no major significant progress has been made yet.

Seoul-Tokyo relations remain badly frayed largely because of Japan's refusal to atone for its past wrongdoings stemming from its colonial rule of the Korean Peninsula from 1910-45. One of the key pending issues is a demand by former Korean sex slaves for an apology and compensation from Japan.

Japan has so far refused to comply with the demand, insisting that the comfort women were recruited by civilian profiteers and its wartime military-led government was not directly involved.

The issue has gained urgency in recent years as the victims are dying off. In 2007, more than 120 South Korean victims were alive, but the number has since dropped to 47, with their average age standing at nearly 90.

Historians estimate that more than 200,000 women, mostly Koreans, were sexually enslaved by Japanese troops during World War II.