Trump is widely expected to make a speech Thursday laying out a new Iran strategy and decertifying the country's compliance with the 2015 nuclear deal. The agreement known as the Joint Comprehensive Plan of Action (JCPOA) gave Tehran sanctions relief in exchange for curtailing its nuclear program. Representative Ed Royce, Republican chairman of the House Foreign Affairs Committee, said the Trump administration should preserve the deal to protect US national security, even though he opposed the deal at the time.

 

"As flawed as the deal is, I believe we must now enforce the hell out of it," Royce said.

 

"Let's work with allies to make certain that international inspectors have better access to possible nuclear sites, and we should address the fundamental sunset shortcoming, as our allies have recognized," he said.

 

Royce took issue with current restrictions constraining Iran's ability to produce fissile material because they begin to sunset in less than a decade.

 

Representative Eliot Engel, the committee's top Democrat, also voted against the deal at the time but said Wednesday that the US must protect the agreement to prevent Iran from becoming a nuclear power.

 

"The administration seems poised to take the first step in withdrawing from the JCPOA," Engel said. "I must say that I view that course as a grave mistake."

 

Engel said the US must "live up to our word."

 

"If we withdraw from the deal now, Iran would be free today from the constraints on their program and the intrusive inspections that the JCPOA puts into place," he said. "They could race headlong toward a nuclear bomb, hold all of the benefits of sanctions relief, and continue fomenting instability across the region."

 

Engel said the US would lose any leverage it has with allies in the deal if it abandons the JCPOA.

 

On Thursday, the committee plans to mark up the Ballistic Missiles and International Sanctions Enforcement Act, a bill introduced by Royce and Engel that would tighten sanctions on individuals and entities supporting Iran's ballistic missile program.

 

Western sanctions that were frozen as part of the JCPOA do not automatically snap back into place as a result of Trump's expected decertification decision.

 

However, the move is seen as a signal that Trump is willing to impose similar sanctions through his own executive action or pressure Congress into doing so through the Iran Nuclear Agreement Review Act of 2015.

 

Analysts disagree on the impact of reimposed US sanctions, especially if European sanctions remain frozen. Some see a major impact on par with the pre-deal sanctions, while others expect many oil traders to find workarounds.