BEIJING, Feb. 7 (Xinhua) -- Romania's recent decision to allow U.S. missile interceptors on its territory was welcomed by Washington, but understandably raised suspicion in Moscow.

Russia was concerned about the U.S. missle shield plan and asked for an explanation from the U.S. side, said the Russian Foreign Ministry in a statement issued Friday.

Analysts say the Romanian decision came at a crucial moment when Washington and Moscow are about to sign a successor document to the expired Strategic Arms Reduction Treaty (START-1). Therefore, the move may upset the thawing Russia-U.S. relations and put their bilateral ties to test.