"For Medvedev, it would be a disaster," he adds. "If START fails, he will immediately face attacks over his policy of making concessions to the US, and we know there are plenty of people here who will say that his decision to cut off arms sales to Iran was against Russia's national interests."
"When we look upon how important Russian support has been" on issues like getting the UN Security Council to approve tough Iran sanctions and setting up a resupply route for NATO troops in Afghanistan through former Soviet territory, "my hope is that because this is a good treaty we should get it done," he said.
Medvedev and Obama will meet again at the NATO summit this weekend in Lisbon, and Russian experts say they hope to hear good tidings about the fate of START by then.
"This treaty is such an important step for our two countries, but to go further down this road we need to see it ratified," says Gennady Yevstafiev, an expert with the PIR Center, an independent Moscow think tank that specializes in nuclear security issues. "On the other hand, how can we trust the US if the president signs an agreement, but Congress says no? A lot of people are watching this very carefully."