President Barack Obama said on Friday he understands why some US lawmakers want to "look tough" on Iran but insisted now is not the time to impose new sanctions on Tehran while it is set to negotiate over a long-term nuclear deal with world powers."There is no need for new sanctions legislation, not yet," Obama told a White House news conference a day after a group of US senators introduced a bill to impose new punitive measures on Iran if it breaks an interim nuclear deal reached last month in Geneva.Obama, who has warned that new sanctions could scuttle the negotiations, said that "if we are serious" about seeking a final nuclear agreement the United States has to act in ways that do not increase Iranian suspicions. The Obama administration is pushing back against a bipartisan group of senators after they introduced a new sanctions bill against Iran on Thursday.At a briefing with journalists, White House press secretary Jay Carney said that the president would veto the bill if it were passed today.The bill would trigger new sanctions against Iran should six months pass without a comprehensive agreement with world powers ending its nuclear program. A veto threat by the president is rare and powerful, but in this case unnecessary: the legislation is unlikely to pass, as it is unlikely to see a vote in the first place. The decision to move forward with the bill by its authors— Senate Foreign Relations Committee chairman Robert Menendez, a Democrat, and Mark Kirk, a Republican— may be more political than practical. With just days left in the congressional session before members recess for the holiday, they have no realistic chance of getting a vote before the new year.Nevertheless, Menendez and Kirk did whip the support of 24 cosponsors across party lines in short order.To the chagrin of those in the White House, the new legislation was introduced before the interim deal forged in Geneva last month had yet been implemented. Menendez's office announced the bill's introduction on the same day that technical talks restarted in Geneva over how to implement the interim deal.State Department deputy spokeswoman Marie Harf said that the Senate action "defies logic.""We strongly oppose the action taken by these members of Congress," Harf said. "It appears in this case, with the introduction of this legislation, that they’ve chosen to ignore the assessment of our negotiators and also our intelligence community, which has said that additional sanctions would make this harder." The Geneva deal agreed upon by Iran and the P5+1 powers— the US, United Kingdom, France, Russia, China and Germany— effectively halts Iran's nuclear program in exchange for modest sanctions relief."I think the Iranians read our press and knew this might be happening," Harf said. "I don't think this was a secret to anyone."The action amounts to an "unnecessary risk threatening negotiations," she added. "Congress can pass new sanctions in 24 hours if they wanted to."Carney said the Obama administration would support new sanctions should Iran fail to comply with the tenets of the Geneva deal, or should six months pass without a comprehensive agreement. But only at that time should sanctions be considered, and at that point, promptly passed and implemented."We don't think it will be enacted, we don't think it should be enacted," Carney said of the bill on Thursday after it was introduced."It is very important to refrain from taking an action that would potentially disrupt the opportunity here for a diplomatic solution," Carney said. "We don't want to see actions that would proactively undermine American diplomacy."