Diplomats, who spoke on condition of anonymity, told foreign media in Kosovo that Rugova's condition was now more serious that it had seemed before.
Rugova, 60, was transferred to the US military base at Landshut, Germany, after he had caught a serious cold.
The Office of the Kosovo President could not confirm media reports. Presidential spokesman Muhamet Hamiti said that a press release on Rugova's condition would be issued after thorough medical examinations were completed.