The US State Department on Sunday officially transferred to American lawmakers the complex text of an Iran nuclear deal, firing the starting gun on what is set to be a bitter Congress battle.

Top US administration officials are girding for a huge fight with the Republican-controled Congress, which, while it cannot modify the terms of the historic deal, can vote to approve or disapprove the accord.

"Day One of the 60-day review period begins tomorrow, Monday, July 20," State Department spokesman John Kirby said, after revealing the bureau had "transmitted to Congress the Joint Comprehensive Plan of Action, its annexes and related materials."

Under the July 14 agreement, Iran has agreed to dismantle or mothball much of its nuclear industry in return for an easing and eventual lifting of biting economic sanctions.

But critics, including Israeli Prime Minister Benjamin Netanyahu, say it still gives the Islamic republic ample chance to cheat, and find a covert way to arm itself with a nuclear bomb.

"This regime has just received the dream deal," Netanyahu said on CBS's "Face the Nation" on Sunday.

The deal, hammered out with Tehran and six world powers over almost two years, "may block or delay Iran's path to one or two bombs for the next few years, assuming they don't cheat, but paves their way to many, many bombs after a decade or so," he added.

He insisted on ABC's "This Week" that it was "a bad deal" and said he would tell visiting US Defense Secretary Ash Carter that Washington and the other powers should "hold out for a better deal."

In duelling appearances with Netanyahu on the Sunday morning US talk shows, US Secretary of State John Kerry and Energy Secretary Ernest Moniz defended the accord which they helped negotiate.

"We'd love to see the Congress listen carefully," Kerry said on CBS, as he prepares to face a Senate panel on Thursday.

"We're going to do our utmost to persuade people," he added, insisting that "this deal will stand ultimately on the fact that there's unprecedented inspection, unprecedented access, unprecedented restraint in their program, which they've agreed to."

And Kerry warned on CNN's "State of the Nation" that the "real fear" of the Middle East "should be that you don't have the deal."

"If Congress doesn't pass this, if Congress were to kill this, then we have no inspections, we have no sanctions, we have no ability to negotiate."