WASHINGTON (Yonhap) -- U.S. Under Secretary of State Wendy Sherman called in both the South Korean and the Japanese ambassadors to Washington for separate meetings on Friday in a possible sign that the U.S. is stepping up efforts to help improve relations between the two key Asian allies.

Sherman met with South Korean Ambassador Ahn Ho-young on Friday morning and discussed various issues, including historical tensions and the North Korean nuclear standoff, for about an hour, a diplomatic source said. She held a similar meeting with Japanese Ambassador Kenichiro Sasae later in the day.

The meetings came days before the three countries are to hold high-level talks during which historical tensions between Seoul and Tokyo are expected to be a key topic. Participants in next week's talks will be U.S. Deputy Secretary Antony Blinken, South Korea Vice Foreign Minister Cho Tae-yong and Japanese Vice Foreign Minister Akitaka Saiki.

Sherman could have used Friday's meetings to preview next week's talks.

Sherman's meeting with Ahn was their first since she caused a firestorm in South Korea with remarks in late February that political leaders should not try to exploit nationalist feelings and "earn cheap applause by vilifying a former enemy."

The remarks were seen as referring to South Korea and China criticizing Japan for refusing to fully atone for its past wrongdoings, such as the country's sexual enslavement of Korean and other Asian women for its troops during World War II.

South Koreans expressed outrage, wondering how the U.S. could blame victims of Japan's militaristic past for the deadlocked situation in relations between South Korea and Japan when Tokyo keeps trying to whitewash and deny responsibility for its wartime past.