BELGRADE, Serbia (AP) — A United States senator has expressed hope that Serbia won't grant diplomatic status to the Russian staff of a controversial facility that some believe is a spy base but that Moscow insists is a disaster relief center.

Wisconsin Republican Ron Johnson, who chairs the U.S. Senate Committee on Homeland Security and Governmental Affairs, said Tuesday that such a move by Serbia would not be in the Balkan country's interest and would send a "very bad signal."

Johnson spoke in Serbia's capital, Belgrade, after talks with Serbia's President Aleksandar Vucic. Serbia is seeking European Union membership, but also has close ties with Russia.

Moscow has denied speculation that the Russian-Serbian Humanitarian Center opened in 2011 is really a station for eavesdropping on Western interests in the Balkans.