The U.S. embassy in Belgrade said there's no need to grant diplomatic status to the Russian staff of the controversial facility in Serbia that some consider a spy base but that Moscow insists is a disaster relief center.

An embassy statement obtained Saturday by The Associated Press said its representatives visited the Nis center, 120 miles south of Belgrade, this week at the invitation of the center's management.

"U.S. representatives were briefed on the current functioning of the center, but saw nothing in the activities that were shown which would indicate a need for diplomatic status," the statement said. "The consistent demands for inviolability for the personnel and premises of the Center only raise question regarding long-term intentions for the facility."

Russia has denied speculation they are eavesdropping on American military interests in the Balkans from the so-called "Russian-Serbian Humanitarian Center," which was formed in 2011. Moscow says the center is only for humanitarian missions.

Serbia has been boosting military and other relations with its traditional Slavic ally Russia, while formally seeking European Union membership. Serbian President Aleksandar Vucic will visit Washington in the next two days for talks with U.S. officials, including Vice President Mike Pence, according to Vucic's office.

The Russian Ministry for Emergency Situations is a partner in the Nis center. The powerful semi-military outfit's activities do include disaster relief, but the agency also carries out jobs for Russia's security services. The ministry has long played a role in Serbia, including de-mining and clearing unexploded ordnance from the 1999 NATO bombing of the country.

European Union officials say if Serbia wants to become a member, as it formally wants to, it will have to join the EU's emergency relief programs and ditch the Russian ones.