Barack Obama caught hinting at concessions to Dmitry Medvedev Mr Medvedev has vowed to respond to the shield's construction by deploying cruise missiles to Russia's westernmost point that could destroy large parts of the shield. Mr Putin, who was last month re-elected to the office he held from 2000 to 2008 after four years as prime minister, made sabre-rattling opposition to the shield a prominent part of his manifesto. Republicans pounced on Mr Obama's remarks as proof that he was secretly planning to give concessions to Moscow if he were returned to the White House for a second term. Reince Priebus, the party chairman, accused Mr Obama of "allowing his political career to dictate national security," adding: "Was he ever going to tell voters?" Mitt Romney, the Republican presidential front-runner, described the comments as a "revealing and unguarded moment." He said in a statement: "President Obama needs to level with the American public about his real agenda." Moscow is seeking a "legal guarantee" that US missile defences would not be directed at Russia. This would require a treaty to be ratified by the US Senate, which would be certain to block such a move. Steven Pifer, the director of the Brookings Arms Control Initiative, said that a re-elected Obama administration might offer to share information on the project with Moscow or even effectively allow Russian officials to inspect the system. "Essentially you say 'here are our plans, here are the number of things we have, and we will keep you updated'," said Mr Pifer. They could also permit official observations of testings. However Mr Obama's opponents would say these put the US on a slippery slope. After Congress last year passed legislation constraining Mr Obama's ability to share classified information on missile defence with Russia, the president issued a statement signalling that he may attempt to get around this, indicating that he sees it as potential leverage for negotiations. Warning that Congress had made it "exquisitely clear" that concessions were unacceptable, Mike Turner, a Republican congressman for Ohio and chairman of the House Armed Services subcommittee said in an open letter: "My colleagues and I will not allow any attempts to trade missile defence of the United States to Russia or any other country." The White House attempted to play down the significance of the comments. Ben Rhodes, a spokesman on security, said that the US was "committed" to implementing the system. "Since 2012 is an election year in both countries, with an election and leadership transition in Russia and an election in the United States, it is clearly not a year in which we are going to achieve a breakthrough," said Mr Rhodes.