By Jim Sciutto
The Obama administration's efforts to negotiate a final deal with Iran over its nuclear program faces a potential new hurdle as the Senate moves toward a veto-proof majority supporting legislation authorizing new economic sanctions on Iran.
The bipartisan proposal introduced by Foreign Relations Committee Chairman Sen. Robert Menendez, D-New Jersey, and Sen. Mark Kirk, R-Illinois, now has 59 senators who have formally committed to support it, a senior Senate aide tells CNN.
But the aide said that the current informal count is even higher - at 77 yes votes - and that more are expected to come on board once the undecided are forced to vote.
The bill could come to the Senate floor for consideration during the week of President Barack Obama's State of the Union address on January 28 or the following week, the aide said.
The proposal would give Obama more than a year to engage in further diplomacy before any new sanctions would kick in against Iran's oil exports and other key areas of its economy. Sanctions would hit sooner if Iran cheats on the interim deal or fails to reach a final accord.
The administration has threatened to veto the legislation if Congress were to approve it now, saying new sanctions would undermine the delicate efforts to forge a lasting deal with Iran.
"Our strong concern is that passage of sanctions at this time would negatively affect and perhaps scuttle the negotiations that are underway and then make it much harder, if not impossible, to achieve our objective peacefully, " White House press secretary Jay Carney said Friday.
In November, six world powers, including the United States, struck an interim deal to limit its nuclear activities in return for a relaxation of sanctions that have crippled the Iranian economy. Envoys from Iran and the European Union have been meeting this week in Switzerland about how to implement that deal.