"Iran has begun to take concrete and verifiable steps to halt its nuclear program," State Department spokeswoman Jen Psaki said, adding it was "an unprecedented opportunity" to resolve concerns over the nuclear program.

Kerry has approved the waiver, which will allow more reliefs to help Iran's crippled economy, and it would be sent to Congress on Monday, she added.

As agreed with world powers under a six-month deal reached on November 24, the US administration "has taken the necessary steps to pause efforts to further reduce Iranian crude oil exports," a separate US fact sheet said.

This will allow the six nations which buy Iranian oil to continue to do so for the duration of the deal.

Sanctions will also be suspended on non-Americans trading in Iran's petrochemical exports, as well as certain trade in gold and precious metals and Iran's automotive sector.

White House spokesman Jay Carney hailed Iran's actions as "an important step forward."

"These actions represent the first time in nearly a decade that Iran has verifiably enacted measures to halt progress on its nuclear program, and roll it back in key respects," he said in a statement.

"Iran has also begun to provide the IAEA with increased transparency into the Iranian nuclear program, through more frequent and intrusive inspections and the expanded provision of information to the IAEA."

Psaki agreed "these actions today are significant steps in our efforts to achieve a diplomatic solution."

"The coming negotiation to reach a comprehensive agreement that addresses all of the international community's concerns will be even more complex, and we go into it clear-eyed about the difficulties ahead," she said.

Psaki also added that today's events have made clear that we have ‘an unprecedented opportunity’ to see if we can resolve our concerns peacefully.

NJF/NJF