Russia and the United States have failed to narrow their differences over a planned US missile shield and stand practically no chance of reaching a compromise at the NATO summit in Chicago in May, a top Russian official said Tuesday. Deputy Defense Minister Anatoly Antonov said Washington is going ahead with its plans for a missile shield in Europe without considering Russian concerns. The US says the NATO missile shield is aimed at deflecting potential missile threats from Iran, but Moscow fears that it will eventually grow powerful enough to undermine Russia's nuclear deterrent. “I think it would be very difficult to achieve any success at the summit,” Antonov said. “As of today, there is no document for the leaders to approve.” NATO has offered Moscow to cooperate on the missile shield. Russia has said the missile shield should be run jointly, a proposal which has been rejected by NATO. Without a NATO-Russia cooperation deal, President Dmitry Medvedev has sought guarantees from the US that any future shield is not aimed at Russia. He has threatened to deploy missiles aimed at the US shield if no agreement is reached. Antonov said any moves “will depend entirely on how the US implements its plans.” “If it conducts the policy of presenting us with a fait accompli, that doesn't show trust and respect for us as partners,” Antonov said. He wouldn't say whether president-elect Vladimir Putin would participate at the NATO summit beginning May 20 after attending the Group of Eight leading industrialized nations summit at Camp David.