WASHINGTON (Reuters) - U.S. Vice President Joe Biden will visit Serbia and Kosovo next week, the White House said on Tuesday.

A White House statement announcing the Aug. 15-17 Balkan tour said Biden would hold meetings with each country's president and prime minister, but did not say what subjects would be discussed.

The United States last month transferred two inmates from the U.S. military prison at Guantanamo Bay, Cuba, to Serbia. U.S. Secretary of State John Kerry thanked Serbia for what he called a "significant humanitarian gesture."

Kerry visited Serbia and Kosovo in December. His stop in Kosovo underscored Western concern over the slow pace of progress 16 years after a U.S.-led NATO air war set the former Serbian province on the road to independence.

Kosovo, a mainly Muslim but secular and staunchly pro-American country, declared independence in 2008.

(Reporting by Mohammad Zargham; Editing by James Dalgleish)