WASHINGTON - Russian President Dmitry Medvedev said on Tuesday that he and Barack Obama have "changed the atmosphere" in Russian-US ties, but demanded more American support on issues from the economy to Afghan drugs.

Medvedev also set boundaries for Russia's backing on sanctions against Iran and suggested an air base in Kyrgyzstan might not be the best tool for stabilizing Afghanistan.

His remarks, delivered at a Washington think tank after a nuclear security summit he called a "complete success," underlined the achievements and the limitations of Obama's campaign to "reset" Russia ties after years of deepening rancor under their predecessors, George W. Bush and Vladimir Putin.