Russia's new president, Dmitry Medvedev, convened a potentially powerful security body for the first time Sunday - leaving out the official long perceived as his rival for the top job. Deputy Prime Minister Sergei Ivanov's name was not on the list of presidential Security Council members released by the Kremlin. Ivanov had been a member of the advisory body under former President Vladimir Putin, whom he served as Defense Minister and then as a first deputy prime minister. Medvedev was also a first deputy prime minister, and the two were long seen as the chief rivals for the mantle of Putin's chosen successor. Putin announced in December that he would back Medvedev in the March presidential vote, which his longtime protege won easily.