WASHINGTON -- Support among Senate members for a new sanctions bill against Iran has doubled since the measure was introduced last month.50 senators across party lines now co-sponsor the Nuclear Weapons Free Iran Act of 2013, according to multiple Senate aides, who expect support to increase in the coming days. That amounts to half of all Senate members, just one shy of the number required for a bill to pass. Senate Foreign Relations Committee chairman Robert Menendez introduced the bill just before Christmas with 25 co-sponsors. The move was an affront to the Obama administration, which fears the bill could derail fragile nuclear talks among Iran, the US and world powers.If enacted, the bill would provide the president with a window of up to a year to negotiate a final settlement with Iran over its controversial nuclear program. Iran would also have to comply with an interim agreement forged between its government and the P5+1 powers— the US, United Kingdom, France, Russia, China and Germany— that effectively halts uranium enrichment and construction on its Arak plutonium reactor in exchange for modest sanctions relief.Should Iran fail to meet either of these terms, new sanctions would trigger against the Islamic Republic that would include harsh penalties for countries still importing Iranian oil, including US allies, requiring they cut at least 30 percent of their purchases within months of enactment.One senior Senate aide told The Jerusalem Post on Tuesday that a vote is "fully expected" on the measure, despite suggestions from the White House that the bill would not reach the floor."We don't think this action is necessary," White House press secretary Jay Carney said on December 19. "We don't think it will be enacted. If it were enacted, the president would veto it.”But another aide familiar with the bill thought a path forward was possible between Senate leadership—including Menendez and senators Charles Schumer and Mark Kirk, who co-authored the bill—and the White House."Rhetoric aside, everyone can get something here," the aide told the Post. "The administration gets up to a year of flexibility to negotiate, Iran gets its limited sanctions relief and Congress gets the insurance policy we've been seeking." In the House of Representatives, Republican leadership scheduled floor time for Iran legislation this month. Democratic whip Steny Hoyer and Republican majority leader Eric Cantor have jointly written a resolution framed in support of the Senate measure.Senator Tim Johnson, chairman of the Senate Banking Committee, which typically reviews sanctions legislation, said on Monday that the bill would not proceed through his committee, and would have to take an alternative route to the Senate floor.Johnson said he believed warnings from US Secretary of State John Kerry that negotiations with Iran would "collapse" if the Senate passed the bill, even if it is "tentative" in nature.