As a November 24 deadline for an historic accord between Iran and global powers looms, Obama said the coming weeks would test the true intentions of the Islamic republic after a decade of stop-start global efforts.
"We presented to them a framework that would allow them to meet their peaceful energy needs," Obama told reporters.
It was the first time the United States has alluded to a completed framework being on the table, and came just days before top diplomat John Kerry holds fresh negotiations with his Iranian counterpart.
If Iran is sincere in not seeking a nuclear weapon, "if that's in fact true, they have an avenue here to provide that assurance to the world community," Obama said.
It would be "a progressive step-by-step verifiable way" which would "allow them to get out from under sanctions so they can re-enter as full-fledged members of the international community."
Iranian leaders have long insisted they are not seeking to develop an atomic bomb, saying the country's nuclear program is solely for peaceful civilian energy needs.
At issue has been how to meet those energy needs, while at the same time cutting off Iran's path to a nuclear weapon.
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But Obama again repeated Washington's long-held insistence that "no deal is better than a bad deal."
"Whether we can actually get a deal done, we'll have to find out over the next three to four weeks," Obama told reporters ahead of weekend talks in Oman between Kerry and Iranian Foreign Minister Mohammad Javad Zarif.
Obama's press conference came a day after the Republican Party seized back control of the US Senate, putting the president's rivals in a powerful position to thwart any deal with Iran by refusing to lift US sanctions.
So far diplomats from the global powers leading the nuclear talks -- Britain, China, France, Germany, Russia and the United States -- have refused to divulge any details of the complex technical negotiations.
But the aim is to draw up ways to cut off any suspect Iranian nuclear activities, such as uranium enrichment, in return for a lifting of crippling international sanctions.
According to The New York Times this week one part of the deal could involve shipping Tehran's huge stockpile of uranium to Russia to be converted into fuel rods for Iran's Bushehr nuclear plant.
Once uranium has been converted into fuel rods, it is difficult to use it as a weapon.
Under an interim deal reached a year ago, Iran agreed to halt uranium enrichment and even reduce some of its stockpile in exchange for the unblocking of about $7 billion in frozen oil revenues to help its economy.