U.S. Vice President Joe Biden is urging wartime foes Serbia and Kosovo to mend ties and normalize relations, a condition for both countries to join the European Union, the Associated Press reports.

Speaking to reporters in Kosovo Wednesday, August 17 after talks with President Hashim Thaci, Biden said, "I know the scars of war are raw ... but reconciliation is necessary."

Kosovo declared independence from Serbia in 2008, but Belgrade does not recognize its former province. However, it has signed a series of EU-brokered deals to regulate relations between the two.

A U.S.-led NATO bombardment in 1999 stopped Serbia's crackdown against ethnic Albanian separatists, ending Belgrade's rule over Kosovo.

Biden offered condolences for those killed in the NATO airstrikes during a visit to Serbia on Tuesday, part of the vice president's 3-day trip to the Balkans.