SOCHI, Russia – President Bush and Russian President Vladimir Putin failed to overcome sharp differences over a U.S. missile defense system, closing their seven-year relationship Sunday still far apart on an issue that has separated them from the beginning.

“Our fundamental attitude toward the American plan has not changed,” Putin said at a news conference with Bush at his vacation house at this Black Sea resort. “Obviously we’ve got a lot of work to do,” Bush said. Despite the impasse, the two leaders agreed that Moscow and Washington would work together closely in the future on missile defense and other difficult issues.

Putin declared there were no breakthrough solutions but said “certain progress is obvious” in the long-running dispute on missile defenses. He was referring to U.S. concessions to assuage Russia’s concerns. U.S. officials said that was what they wanted to hear him say.

Bush also conferred with Putin’s hand-picked successor, Dmitry Medvedev, but did not claim gaining any insight into his soul, as he had with Putin upon their first encounter. He pronounced Putin’s protege “a straightforward fellow” and said he was eager to work with him.

Putin was asked whether he – or Medvedev, the president-elect – would be in charge of Russia’s foreign policy after May 7, when Putin steps down as president and is expected to be named prime minister.

Putin said Medvedev would be in charge, and would represent Russia at the Group of Eight meeting of industrial democracies in July in Tokyo. “Mr. Medvedev has been one of the co-authors of Russia’s foreign policy,” Putin said. “He’s completely on top of things.”

National Security Adviser Stephen Hadley, when asked later whether he thought Putin actually was going to cede authority on Russian foreign policy to Medvedev, said: “My guess is that these two men who have worked very closely together for now almost two decades will have a very collaborative relationship. That seems to be a good thing, not a bad thing.”

Hadley, who spoke with reporters aboard Air Force One on the way to Washington, also said he didn’t see any prospect of a breakthrough on missile defense before Bush leaves office. “They can leave that to their prospective successors,” he said.