Congress wants a say on both matters, given the far-reaching ramifications for possible deals involving two of America’s biggest overseas adversaries.

Absent a ceasefire, Senate Majority Leader John Thune (R-SD) is threatening to slap a new round of sanctions and tariffs on Russia via a bipartisan bill from Sens. Lindsey Graham (R-SC) and Richard Blumenthal (D-CT). It has a veto-proof majority of sponsors with 82 senators in a rare show of overwhelming bipartisanship. The measure would impose more economic sanctions that include a 500% tariff on goods from countries that buy Russian oil in a bid to force Moscow to strike a peace deal.

“The Senate is prepared either way,” Graham warned in a “letter to the editor” responding to an op-ed from the Wall Street Journal Editorial Board. “The consequences of [Russia’s] barbaric invasion must be made real to those that prop it up. If China or India stopped buying cheap oil, Mr. Putin’s war machine would grind to a halt.”

There’s a companion bill in the GOP-led House, but neither chamber would act until next week at the earliest after returning from a weeklong Memorial Day recess. Sen. Kevin Cramer (R-ND), who, like Graham, is a close Trump ally, told a small group of reporters at the Capitol Tuesday that he, too, was prepared for Congress to act before the president.

Other key Republicans are also urging action.

“I’ve had enuf of Putin killing innocent ppl,” Sen. Chuck Grassley (R-IA), who’s third in line to the presidency as Senate president pro tempore, wrote in a Memorial Day tweet. “Pres Trump Take action AT LEAST SANCTIONS.”

Trump posted on Truth Social in recent days that Putin is “playing with fire” and has “gone absolutely CRAZY!” for continued strikes against Ukraine.

On Iran, there are warnings from Republicans that any new nuclear deal struck between Trump and Tehran would need Senate approval. Any treaty struck between the United States and Iran would require a two-thirds majority vote in the upper chamber, as laid out in the Constitution and noted by Sen. Mike Lee (R-UT).

The red line for both sides is whether Iran should be able to continue uranium enrichment, a material used for nuclear weapons. But just as the U.S. has high stakes to limit Iran’s nuclear capabilities and try to strengthen stability in the region, Tehran striking a deal could mean the loosening of crippling oil sanctions.

Congressional Republicans want Iran‘s nuclear program to be fully dismantled and have pressured the Trump administration to make such demands in response to mixed messages from U.S. officials on the endgame with Tehran.

“I want to encourage the president to continue to apply maximum pressure, and make sure that we are not allowing Iran to have any sort of nuclear program,” Sen. Pete Ricketts (R-NE), a member of the Foreign Relations Committee, recently told the Washington Examiner. “We’re not signing off on that, where they can then get enough materials to create a bomb.”

Several rounds of recent talks under Trump’s second term between Iranian and U.S. delegations have yet to produce an agreement, despite the president’s recent trip to other Middle Eastern nations.  

TRUMP SHARPENS PUTIN CRITICISM IN WARNING AS HE WEIGHS SANCTIONS ON RUSSIA: ‘PLAYING WITH FIRE!’

“Zero nuclear weapons=we Do have a deal. Zero enrichment=we do NOT have a deal,” Iranian Foreign Minister Abbas Araghchi recently posted to social media. “Time to decide.”

David Sivak contributed to this report.