The chairman of the House Committee on Foreign Affairs blasted the Iran deal during a hearing with top administration officials on Tuesday.
"If this agreement goes through, Iran gets a cash bonanza, a boost to its international standing, and a lighted path toward nuclear weapons," said Chairman Ed Royce (R-Calif.) in prepared remarks.
"The U.S. still wields the most powerful economic sanctions in the world — sanctions Iran desperately needs relief from — sanctions that would continue to deter countries and companies from investing in Iran," he continued.
Secretary of State John Kerry, Energy Secretary Ernest Moniz, and Treasury Secretary Jack Lew are testifying before Royce's committee as lawmakers weigh the nuclear deal with Iran.
The deal, negotiated by the U.S. and world powers with Tehran, would lift economic sanctions in exchange for limits on Iran's nuclear program.
Congress is expected to vote on the deal in September, with Republicans all but certain to reject the agreement in a joint resolution of disapproval. Such a resolution would prevent U.S. sanctions from being lifted as part of the deal to get Iran to limit its nuclear program.
But President Obama has vowed to veto any move to block the deal and opponents of the Iran agreement would need two-thirds in both chambers to override.
In his opening statement, Royce acknowledged that rejecting the deal would "roil the diplomatic waters," but argued, "These are about as high stakes as it gets.
"With sweeping sanctions relief, we have lessened our ability to challenge Iran’s conduct across the board. As Iran grows stronger, we will be weaker to respond," he warned.
"So instead of us considering a verifiable, enforceable, and accountable agreement, we are being asked to consider an agreement that gives Iran permanent sanctions relief for temporary nuclear restrictions.
"Should Iran be given this special deal?" he asked.
In his remarks, Royce specifically criticized key elements of the deal.
He said Iran would not be required to dismantle key bomb-making technology, is permitted to keep a vast enrichment capability, and would be allowed to continue research and development to gain an industrial-scale nuclear program once the agreement begins to expire in as little as 10 years.
"That’s a flash in time, and then Iranian obligations start unwinding. Does this make the world more secure?" he asked.
Royce also said the inspection regime "came up short" from "anywhere, anytime" access to Iran's nuclear facilities and criticized the removal of restrictions on Iran's ballistic missile program and conventional arms.
Royce also slammed the administration for letting the United Nations vote on the deal before Congress.
He said the administration "went against bipartisan calls and gave Russia and China and others at the U.N. Security Council a vote on this agreement before the American public."
"That’s backwards — and wrong," he said.
The committee's top Democrat, Rep. Eliot Engel (D-N.Y.), also criticized the deal, but urged his colleagues to take "full advantage" of the 60 days Congress has in which to consider it.
He also urged lawmakers to consider the alternative if they rejected the deal.
"Would renewed pressure bring the Iranians back to the table, if this deal fails?" he asked.
Still, Engel listed a litany of concerns he had about the deal. He said that under the deal, Iran could have more than a month to refuse international inspections of some sites.
"That potential length of time gives me pause," he said. He also expressed concern that some military facilities are "off-site" from inspectors.
He also said he was "troubled by reports" on side deals made with the International Atomic Energy Agency on how Parchin, a military site, would be inspected.
And Engel expressed concern that restrictions on ballistic missiles and conventional arms would be lifted in five to eight years.
"I'd like to understand how we allowed this to happen," he said.
Engel also questioned what Iran would do when sanctions are phased out, resulting in billions of dollars in relief.
"My fundamental concern is that 15 years from now, Iran will be off the hook," he said.