The Obama administration says it is committed to diplomacy with Iran, but is reviewing the possibility of imposing enhanced sanctions. U.S. officials stress they will not wait forever for Tehran to come clean about its nuclear ambitions.
The White House says the latest round of multilateral talks on the Iranian nuclear dispute began well. Officials say they are now waiting to see if Iran follows through on the pledges made Thursday in Geneva.
U.S. Ambassador to the United Nations Susan Rice says the onus is on Tehran to adhere to the commitments it has made.
"If it does not, time is short. We are not interested in talking for talking's sake," said Rice. "We are not interested in interminable negotiations. They have to demonstrate conclusively that their program is for peaceful purposes."
During an appearance on the NBC television program Meet the Press, Rice declined to discuss specific deadlines. But she said Iran has - in her words - a "finite period" to completely open ichallenging the Iranians with some deadlines and ultimatums, quite frankly."
Democrat Evan Bayh of Indiana is the author of one of several bills pending in the U.S. Senate that would clear the way for tougher American sanctions on Iran. He also appeared on Fox News Sunday.
"I think we need to give them a matter of weeks to come clean on the inspections and actually send the uranium out of the country,"said Bayh. "I think we have got to have firm deadlines - the sooner the better - and real consequences if those deadlines are not met."
Bayh said it is important to get all these sanctions in place to raise the cost of misbehavior for Iran.