But U.S. officials say that won't be so easy, with strong enforcement still in place, along with the most damaging of the sanctions.

Iran analyst Ali Vaez of the International Crisis Group agrees.

“The most important part of the sanctions regime, the crown jewels, which are the oil and financial sanctions, will remain in place. And therefore Iran will have the motivation to come back and negotiate the comprehensive agreement, which is much more difficult to negotiate and would require much more painful concessions,” said Vaez.

Indeed, the impact of the sanctions on ordinary Iranians is believed to be what propelled the relatively moderate candidate, Hassan Rouhani, to the presidency in last May's election, making this accord possible.

The former British ambassador to Iran, Richard Dalton, believes Iranian officials, including Supreme Leader Ayatollah Ali Khameini, have made a strategic decision to do what is necessary to put the nuclear dispute, and the economic sanctions, behind them.

“They will not be saying to themselves, 'We just have to sit this one out and we will emerge with an economy that can trade with the rest of the world freely.' I believe they will go all out in this six-month period to achieve a comprehensive agreement,” said Dalton.

But that doesn't mean it will be easy. Iran will be asked to give up much of the nuclear fuel enrichment program it has built over many years at great expense, and to allow intrusive inspections to prove it is not secretly trying to build a nuclear bomb.