Chairman of the Senate Foreign Relations Committee Bob Corker (R-Tenn) speaks with Sen. Marco Rubio (R-Fla.). Both are sponsoring a new bipartisan bill to impose sanctions on Iran. EPA/MICHAEL REYNOLDS

After more than a year of wrangling, senators announced a bipartisan bill Thursday to impose mandatory sanctions on Iran over its spate of ballistic missile tests and support for a group that President Trump may soon dub a terrorist organization.

The measure from top Republicans and Democrats on the Senate Foreign Relations Committee comes despite Iranian Ayatollah Ali Khamenei’s repeated warnings that expanding sanctions against Iran would jeopardize the nuclear deal struck in 2015 – a deal that Trump promised to undo during his presidential campaign.

Leading Democrats resisted an effort last year from Chairman Bob Corker (R-Tenn.) and high-ranking Democrat Robert Menendez (D-N.J.) – both of whom opposed the Iran deal – to impose similar sanctions over fears that it would put the nuclear deal in a precarious position. The Obama administration also opposed efforts to expand sanctions against Iran, over fears it could adversely affect the controversial deal.

But since before the deal was implemented, members of both parties have clamored for stricter tools to sanction Iran over its repeated ballistic missile tests and the activities of the Iran Revolutionary Guard Corps. Lawmakers argue the military outfit — which has enormous political influence in Iran  – functions as Iran’s terror-promotion arm, through the training and support it offers other groups like Lebanon’s Hezbollah, which the United States has already designated as a terrorist organization.

Corker and Menendez tried to tie their sanctions push to a must-pass ten-year extension of existing Iran sanctions, but came up short when Democrats resisted portions of the package they worried could undermine the nuclear deal.

Some of those provisions been left on the cutting room floor in the latest version of the Iran Sanctions legislation, unveiled Thursday.

They include the elimination of a report on the value of the sanctions relief Iran received in exchange for giving up its nuclear program under the pact; a focus on outlawing off-shore, third-party dollar transactions, and language that would have prevented the administration from using its case-by-case national security waiver to enter into any international agreements with Iran. Democrats saw the last piece as “antagonistic toward the Obama Administration, even after the fact,” said an aide to Sen. Ben Cardin (D-Md.), the ranking Democrat on the Foreign Relations Committee.

The aide added that those changes, which Cardin worked to strip from the deal, were critical for getting his boss – and several other Democrats – to sign on to the bill.

Democrats now supporting the legislation includes senators like Menendez and Cardin, who voted against the Iran nuclear deal, but also several senators who supported it, including Sens. Bob Casey (D-Pa.), Michael Bennet (D-Colo.), Richard Blumenthal (D-Conn.), Chris Coons (D-Del.) and Joe Donnelly (D-Ind.).

It’s unclear whether these changes will satisfy Tehran that the bill does not jeopardize the nuclear deal. Iran has argued that it has the right to conduct ballistic missile tests under the nuclear deal, which slightly watered down the legal prohibition by U.N. resolutions  preventing Tehran from pursuing any nuclear-related activities – such as ballistic missile tests. Under the Iran deal, Iran is simply called upon not to engage in the practice.

Iran’s leaders have not yet weighed in on the legislation.

Still, the bipartisan deal still has the vigorous support of some of the Senate’s hardest-line Republicans when it comes to Iran, including Sens. Marco Rubio (R-Fla.), Tom Cotton (R-Ark.) and James Risch (R-Idaho), in addition to Corker, Dan Sullivan (R-Alaska) and Todd Young (R-Ind.). In 2015, all Republicans voted against the Iran deal – and see in Trump a chance to punish Iran for what it counts as infraction of it.

“The president has said he’s putting Iran on notice, and passing this bill would be an unmistakable sign of resolve,” Cotton said in a statement. “We will not tolerate Iran’s pursuit of supremacy in the Middle East or its sponsorship of terrorism, and we will make the regime in Tehran pay a steep price for its dangerous behavior.”