Washington's continued efforts to build a missile defense shield in Europe have complicated nuclear arms reduction talks with Russia, Russia's deputy prime minister said on Saturday.

"It is impossible to talk seriously about the reduction of nuclear capabilities when a nuclear power is working to deploy protective systems against vehicles to deliver nuclear warheads possessed by other countries," Sergei Ivanov said at an international security conference in Munich.

Russia and the United States are in talks to replace the Strategic Arms Reduction Treaty (START 1), the cornerstone of post-Cold War arms control, which expired in December with a new deal.

Russia on Friday expressed concerns about Romania's decision to host missiles as part of a U.S. missile defense shield to protect European allies from possible Iranian attacks, and Foreign Minister Sergei Lavrov demanded "clarifications."

The planned deployment in Romania comes after President Barack Obama scrapped plans for a radar and interceptor missiles in the Czech Republic and Poland, which Russia fiercely opposed as a national security threat and a blow on its nuclear deterrent. Moscow threatened retaliatory measures.

Obama and Russian leader Dmitry Medvedev pledged at their first meeting in April 2009 to replace the START I treaty as part of broader efforts to "reset" bilateral ties strained in recent years.

Last week, they ordered a speedy completion of the new nuclear arms reduction deal.

MUNICH, February 6 (RIA Novosti)