People queue to push a symbolic Reset Button for US - Russian relations near a life-size cardboard cutout of U.S. President Barak Obama and US flag in downtown Moscow on Friday, July 3. AP MOSCOW (AP) - A top Russian diplomat says the signing of a key U.S.-Russian nuclear arms control treaty, expected to take place during President Barack Obama's visit to Moscow next week, may be delayed.

Deputy Foreign Minister Sergei Ryabkov told Ekho Moskvy radio Saturday that the signature of the successor pact to the 1991 START treaty might be postponed until December.

He said the signature is linked to Moscow's opposition to U.S. plans to install missile defense facilities in Eastern Europe.

Washington says the facilities are aimed at potential threats from Iran, while Moscow insists they could destabilize the strategic nuclear balance.

The START treaty envisages cuts in warheads from the current 1,700-2,200 to about 1,500 and expires in December.