Senate Foreign Relations Committee Chairman Sen. Bob Corker, R-Tenn., right, talks with the committee’s ranking member Sen. Ben Cardin, D-Md. on Capitol Hill. The two are working on a package of new sanctions against Iran, the first such bipartisan effort since the nuclear deal was completed. (AP Photo/Susan Walsh)

After months at odds, leading Democratic senators have formally joined forces with Republicans to design new congressional sanctions against Iran, spurred by a desire to strongly reject Tehran’s most recent reported ballistic missile tests.

Senate Foreign Relations Committee Chair Bob Corker (R-Tenn.) and ranking member Ben Cardin (D-Md.) are preparing legislation to slap additional sanctions on Iran in response to a recent spate of ballistic missile launches. While the tests do not themselves violate the Iranian nuclear deal that took effect in January, officials believe they fly in the face of other international prohibitions and weaken the spirit of compliance needed to sustain the nuclear pact.

The senators are also negotiating a way to extend the current regime of sanctions under the Iran Sanctions Act past the end of the year, and possibly increase sanctions against Tehran for other conventional weapons and terrorist activities as well.

They are looking for a “sweet spot,” Corker said, “to see what kind of legislation is passable.”

If the Senate can produce a package of sanctions, it stands a good chance of getting an audience in the House, where Speaker Paul Ryan (R-Wisc.) said Tuesday that Congress would “continue to press for new sanctions against Tehran” in light of the most recent ballistic missile tests.

But Iran sanctions may not come together as quickly as ones that passed recently by a large bipartisan margin against North Korea.

While the latest ballistic missile test “accelerated” discussions, Cardin wouldn’t guess at an immediate timeline, remarking only that lawmakers “have the calendar year” to take action before the only hard deadline ahead of them: The end of 2016, when the Iran Sanctions Act (ISA), the bedrock for U.S. sanctions against Iran’s nuclear, missile, and terrorist activities, expires.

Corker and Cardin’s intensified discussions explain a delay over measures that Corker and Sen. Robert Menendez (D-N.J.), the committee’s former top Democrat, said they planned to unveil last month. Both senators were vocally against the Iran nuclear deal.

Cardin, the committee’s current ranking member, was not originally a part of those efforts. As recently as last month, Cardin was still promoting a bill introduced last fall to create an expedited pathway for new Iran sanctions, among other things.

He too voted against the nuclear deal, but has urged lawmakers to accept and support it since Congress effectively allowed the pact to proceed in September.

Since the nuclear pact was implemented, Tehran’s aggressive moves, particularly concerning ballistic missile tests, have inspired plenty vitriol in Congress, but it has been spewed primarily along party lines.

The vast majority of Democrats, including party leaders, refused to join Republican efforts in the House and Senate to stymie the implementation of the deal, and no Republicans crossed the aisle to support Cardin’s measure to keep up pressure on Iran.

Though Republicans and Democrats were both frustrated with the administration’s slow response to the ballistic missile tests, they made their appeals mostly separately, sending letters that were largely co-signed only by members of one party. And while a few Democratic proposals to enable unspecified sanctions against Iran did procure some low-level House Republican support, they never advanced to the floor.

.And while a few Democratic proposals to enable unspecified sanctions against Iran did procure some low-level House Republican support, they never advanced to the floor.

But as Tehran continues its weapons tests undeterred, congressional leaders are hoping to echo the cooperative model they established when Congress overwhelmingly passed stiff, mandatory congressional sanctions against North Korea after a nuclear weapons test earlier this year.

“This nation speaks best when we speak with a unified voice,” Cardin said. “There may be disagreement on the [Iran nuclear deal], but there should be no disagreement as to preventing Iran’s proliferation desires,” Cardin said.

Cardin nodded to the recent North Korea sanctions as a successful example of how Congress “led,” and the administration and the international community soon followed suit.

Thus far, the Obama administration has only issued sanctions against 11 individuals involved in Iran’s ballistic missile program. Sen. Kelly Ayotte (R-N.H.) today said those sanctions are “proving to be anemic, given [Iran’s] continuing testing of ballistic missiles.”

Though Cardin said he expects the administration to come down harder on  the ballistic missile program, he signaled that Congress should move forward with its own punishment.

“Every administration wants as much discretion as possible. On Iran, I think it’s important Congress speaks with a very strong, clear voice,” Cardin said. “It is important that Congress be pretty strong in the way that we make it clear that we won’t tolerate ballistic missile violations by Iran.”