US: Iran sanctions will be removed in phases

US Secretary of State John Kerry (2ndL), Iranian Foreign Minister Javad Zarif (2ndR) and other wait to start a meeting during nuclear talks on March 29, 2015 in Lausanne, Switzerland (AFP Photo/Brendan Smialowski)

Washington (AFP) - 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.