France's Foreign Minister Laurent Fabius on Thursday told lawmakers that the sides involved in the Iran nuclear deal negotiations still need to hash out a number of key issues.

�Subjects still remain that we aren�t agreed on, notably on economic sanctions, and the Supreme Leader has made statements that show there is still a lot of work to be done,� Fabius said according to Reuters.

�We are going to keep the position we have held from the beginning, which is constructive but extremely demanding,� Fabius said. �If it�s possible, we want an agreement, but it needs to ensure that nothing remains in the shadows.�

The United States warned Thursday that sanctions on Iran will be lifted in stages as a nuclear deal is implemented, after Tehran demanded they be removed as soon as it comes into force.

"We're not going to respond to every public statement made by Iranian officials or negotiate in public," State Department spokesman Jeff Rathke said.

"Sanctions will be suspended in a phased manner upon verification that Iran has met specific commitments under a finalized joint comprehensive plan of action."

Earlier, Iran's President Hassan Rouhani had declared that Iran would not sign any final nuclear agreement unless "all economic sanctions are totally lifted on the same day."

But Rathke insisted that the framework agreement agreed on April 2 between Tehran and six world powers including Washington foresees a gradual lifting of international sanctions.

"The process of sanctions suspension or relief will only begin after Iran has completed its major nuclear steps and the breakout time has been increased to at least a year," he said, referring to the estimated time it would take Iran to deploy a nuclear weapon.

"So that's consistent with what we said over the last week or so, and that was agreed upon by all the parties in Lausanne," he said.

Under the outline agreed with Britain, China, France, Germany, Russia and the United States -- Iran must slash its array of nuclear centrifuges in exchange for a suspension of sanctions. Centrifuges enrich uranium to a level at which it can fuel power plants or, at greater levels of purity, form the core of a nuclear bomb.

The outline deal was hailed as a major breakthrough in a 12-year crisis over Tehran's alleged quest for nuclear weapons, and has raised hopes among Iranians of a lifting of economic sanctions. But a full detailed agreement between the parties has yet to be drafted, with June 30 set as the new deadline for the ongoing negotiations.

Poll: 68% of Americans don't believe Iran
Meanwhile a new survey shows that 68 percent of Americans do not believe Iran will uphold its part of a final nuclear accord with six major powers.

Only a quarter of those surveyed in NBC News' poll, which was conducted online April 6-8 and released on Thursday, said they trusted the Islamic Republic "to abide by a nuclear agreement."

53% of respondents said Iran's nuclear program constitutes a major threat to the United States. 37%, by comparison, said it was a minor threat, while 8% said it was no risk whatsoever.

Nearly two thirds of the 2,052 adults surveyed said they felt the US was heading in the wrong direction.

The poll also found that some 51% of Americans approved of "the way Barack Obama is handling his job as president" compared to 48% who disapproved.

By i24news