WASHINGTON ― President Donald Trump’s former acting treasury secretary warned lawmakers that an Iran sanctions bill under consideration in the Senate Foreign Relations Committee could undermine the Iran nuclear agreement and hurt U.S. relations with allies.

The legislation as currently written would “provoke a terrible reaction in Iran and with our allies, as it would be seen as contrary to at least the spirit of the Joint Comprehensive Plan of Action,” Adam Szubin wrote Friday in a letter to committee members.

Szubin, who left government in February, led U.S. sanctions policy against Iran in his previous role as Treasury Department acting under secretary for terrorism and financial intelligence. The Treasury Department has cited this effort as a key reason Iran agreed to an international deal that rolled back its nuclear program in exchange for sanctions relief.

Though Szubin was nominated for the job by former President Barack Obama, he is considered hawkish on Iran and has pushed for aggressive enforcement of sanctions. Trump asked Szubin to serve as acting head of the Treasury Department until Secretary Steve Mnuchin was confirmed.

The Senate legislation, called the Countering Iran’s Destabilizing Activities Act, was introduced in March and has broad bipartisan support. Twenty-nine Republicans and 14 Democrats have signed on as co-sponsors. But Szubin’s letter is likely to carry significant weight with lawmakers.

“It’s certainly a letter to take note of and will be read seriously,” a committee aide told HuffPost.

The Senate’s sanctions bill in its current form “would contribute no benefit, as it would impose no additional pressure on Iran’s malign activities outside the nuclear space,” Szubin wrote. “As such, I think it would be harmful to our interests to pass this bill.”

He recommended either scrapping the legislation or making two changes:

Removing a clause that would impose new sanctions on anyone the president determines “poses a risk of materially contributing” to Iran’s ballistic missile program. That change would leave in place language calling for sanctions on anyone who has “materially contributed” to the program.

Removing a section that would create new conditions for the lifting of sanctions related to Iran’s ballistic missile program. This section would include sanctions that the U.S. is obligated to lift in the future as part of the nuclear deal. Lawmakers also could add an exemption stating that sanctions would be lifted as required by the nuclear accord, Szubin wrote.

An aide to Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) declined to comment on whether he was open to any of Szubin’s suggestions. Instead, the aide pointed to the bill’s broad bipartisan support, and said the chairman “looks forward to the committee advancing it to the Senate floor in the coming weeks.”

Shortly after the sanctions bill was introduced in March, seven foreign policy heavyweights who served in the Obama administration voiced concerns similar to Szubin’s. The experts, who served in the National Security Council, State Department, Pentagon, and CIA, additionally objected to language in the bill they argued would likely lead the president to designate Iran’s Revolutionary Guards, or IRGC, a terrorist group.

The Trump administration has already considered an executive order designating the organization a terrorist group. Officials from the State Department and Pentagon warned that the designation could complicate the U.S. fight against ISIS in Iraq, where IRGC-backed groups are also fighting ISIS.

The Senate Foreign Relations Committee is expected to hold a markup session to consider changes to the bill at the end of May. The markup will likely come days after the May 19 presidential election in Iran, where current President Hassan Rouhani faces a tough re-election challenge from more hard-lined candidates.

Sen. Ben Cardin (Md.), the ranking Democrat on the Foreign Relations Committee, told reporters last month that the timing of the legislation was unrelated to elections in Iran.

Trump, who during the campaign described the nuclear accord as “the worst deal ever negotiated,” has said he will look for ways to renegotiate the agreement. Secretary of State Rex Tillerson certified Iran’s compliance with the deal last month ― but added that Trump had ordered an inter-agency review to evaluate whether the U.S. should continue to waive sanctions pursuant to the agreement.

Read Szubin’s letter here: