The President of Kosovo, Ibrahim Rugova, is undergoing medical tests at a US military hospital in Germany amid reports that he is seriously ill.
His spokesman Muhamet Hamiti said the tests would help doctors decide on appropriate treatment. But he refused to specify the president's illness.
Mr Rugova, 61, was re-elected last October. He was flown to Landstuhl near Frankfurt on Saturday.
He was said to be ill with flu last week and cancelled some engagements.
His Democratic League of Kosovo (LDK) party won legislative elections in October 2004.
Kosovo has been under United Nations administration since 1999, when a Nato bombing campaign against Serbia stopped Serb forces expelling the ethnic-Albanian majority during an Albanian separatist insurgency.
Mr Rugova, seen as a moderate ethnic Albanian leader, led passive resistance to Serbian rule in the 1990s.
Kosovo's ethnic Albanian majority wants independence, while Serbia fiercely opposes the idea.
Mr Rugova has long campaigned for Kosovan independence