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Washington • A bipartisan group of 26 senators introduced legislation Thursday that threatened new sanctions against Iran, dismissing warnings from the White House that such a move could scuttle efforts to peacefully resolve the dispute over Iran's nuclear program.

The bill, called the "Nuclear Weapon Free Iran Act of 2013," drew a rebuke from the Obama administration and highlighted deep divisions among Senate Democrats on whether to heap new pressures on Tehran's government while sensitive diplomacy is underway. Hours after the bill's introduction, a separate group of senior Democrats revealed in a letter that U.S. intelligence agencies had cautioned lawmakers in private briefings about the consequences of new sanctions. A Dec. 10 intelligence assessment had concluded that new punitive measures would "undermine the prospects for a comprehensive nuclear agreement with Iran," according to the letter, signed by 10 Democrats.

The escalation in the fight over sanctions comes less than four weeks after diplomats from Iran and six world powers signed a historic accord in Geneva that temporarily freezes key parts of Tehran's nuclear program in return for short-term relief from some economic sanctions. Negotiators set a six-month deadline for hammering out a permanent treaty that would set strict limits on Iran's nuclear capabilities.

The measure introduced Thursday, if approved, would impose harsh new sanctions on Iran's petroleum industry while also threatening U.S. allies and partners with financial restrictions unless they sharply curtail trade with Iran. The sanctions would go into effect if Iran violates the terms of the temporary accord reached last month or if it fails to reach a permanent agreement with world powers in a timely manner.

Sponsors of the bill said the measure would increase U.S. leverage as its diplomats continue to work toward a permanent deal. But White House officials had pushed hard to delay the bill's introduction, saying that even the threat of new sanctions could cause the fragile negotiations to collapse.

Iran has warned that any additional U.S. sanctions during the ongoing nuclear talks could doom chances for a deal. Iran's diplomatic team briefly walked away from a round of technical negotiations last week after the Obama administration took action to enforce existing sanctions against the Islamic republic.

"We have made very clear to them that we do not believe now is the time to pass any additional, new sanctions through Congress," White House press secretary Jay Carney told reporters. "We don't think it will be enacted; we certainly don't think it should be enacted."

A key Republican sponsor of the bill, Sen. Mark Kirk of Illinois, said the threat of new sanctions was needed to "protect the American people from Iranian deception."

"The American people rightfully distrust Iran's true intentions, and they deserve an insurance policy to defend against Iranian deception during negotiations," Kirk said.

The letter from the 10 Senate Democrats urged Majority Leader Harry Reid, D-Nev., not to allow the measure to come up for a vote.

"We believe that new sanctions would play into the hands of those in Iran who are most eager to see the negotiations fail," said the letter, whose signatories included Sens. Carl Levin of Michigan and Dianne Feinstein of California.

The bill's prospects appear uncertain at best. Even if Reid allows the bill to come to the floor and it passes, it will have to be reconciled with a far harsher House version passed in the summer. Even if those hurdles are cleared, the legislation is still likely to face a White House veto.

"The president has made clear that if it did come to a vote and passed, he'd veto it," said a senior administration official who spoke on the condition of anonymity about relations with Congress.

"The goal should be for the negotiations to succeed. This would make that far less likely," the official added.