President Trump and Russian President Vladimir Putin. (Don Emmert and Natalia Kolesnikova/AFP/Getty Images)

Three Republican senators are supporting legislation aimed at blocking President Trump from dismantling sanctions against Russia if the president intends to go down that path.

But so far, GOP leaders haven’t signed on to the plan.

Sens. Lindsey O. Graham (S.C.), John McCain (Ariz.) and Marco Rubio (Fla.), the three Republican sponsors of the measure giving Congress a chance to stop the rollback of sanctions, are emerging as a go-to troika on measures to contain Russia at a time when Trump faces accusations that he is acting far too cozy with President Vladimir Putin.

Graham, McCain and Rubio are also the three earliest Republican sponsors of language introduced last month to impose broader mandatory sanctions against Russia. And they were the last GOP members to agree to support Rex Tillerson’s bid to become secretary of state, over concerns about his ties to the Kremlin.

“Russia has done nothing to be rewarded with sanctions relief,” Graham, who spearheaded the new push, said in a statement. “To provide relief at this time would send the wrong signal to Russia. . . . Sanctions relief must be earned, not given.”

But the new bill may never make it to the floor. Two key Republicans are noticeably absent from its list of supporters: Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) and Senate Majority Leader Mitch McConnell (R-Ky.).

Tensions between congressional Republicans and the Trump administration over Russia are rising as the president continues adopting an accommodating stance toward the Kremlin. Many lawmakers assumed that once he took office, Trump’s position toward Russia would harden. But the administration’s recent signals have some worried that Trump and Tillerson may try to relax sanctions against Russia over its annexation of Crimea, interference in Ukraine’s ongoing civil war, and alleged hacks tied to the 2016 election.

Trump’s interview over the weekend with Fox News didn’t help matters. In it, the president dismissed Fox News anchor Bill O’Reilly’s designating Putin “a killer” over his reputation for extrajudicial murders with the following retort: “There are a lot of killers. We have a lot of killers. . . . You think our country is so innocent?”

Graham and the Senate Foreign Relations Committee’s ranking Democrat, Benjamin L. Cardin (Md.), are leading a group of six senators who unveiled legislation Wednesday to let Congress vote on any presidential attempt to roll back Russia sanctions before the sanctions can take effect. The measure also codifies existing Russia sanctions the Obama administration imposed by executive order.

The legislation is fashioned after a 2015 bill that gave lawmakers an opportunity to block the Iran nuclear deal. Senators approved the bill to give themselves a review role by a vote of 98 to 1 — though in the end, opponents were not able to muster enough votes to stop the deal from coming into force.

“Regardless of how you feel about Russia and whether sanctions are effective or how they should be imposed, I think almost every member of the Senate believes that Congress needs to be engaged in that discussion,” Cardin told reporters Wednesday. “This is basically to reestablish ourselves.”

McCain insisted lawmakers must review any decision that “would impact our ability to hold Russia accountable for its flagrant violation of international law and attack our institutions.”

But Democratic leaders are also sounding a cautious note.

According to Democratic aides, Senate Minority Leader Charles E. Schumer (D-N.Y.) – an early champion of giving Congress the power to veto reducing Russia sanctions — removed his name from the list of sponsors to Wednesday’s bill over concerns that without McConnell’s endorsement, the matter would become too politicized to win support.

Republican leaders are aware that many Republicans may be reluctant to openly cross Trump so early in his presidency, even if they believe sanctions must be kept in place. They initially balked at calls to investigate potential links between the Trump campaign and the Russian government, though the House and Senate’s intelligence committees are now exploring such allegations.

Leaders and several rank-and-file Republicans have also shied away from a new measure to step up Russia sanctions in response to Moscow’s alleged hacks of certain Democratic figures and coordination with WikiLeaks to release stolen information during the 2016 elections.

But Trump’s Fox News comments have not helped him.

Since then, Republicans from across the political spectrum have stepped up their efforts to insist the Trump administration stand by Russian dissidents being targeted by the administration, focusing particular attention on activist Vladimir Kara-Murza, who was allegedly poisoned two years ago and recently returned to the hospital with similar symptoms.

Senators who raised Kara-Murza’s case include noted Trump critics such asMcCain, who is leading the charge among Republicans to expand mandatory sanctions against Russia. He used a floor speech Tuesday to tear into attempts to draw “moral equivalence between that butcher and thug and KGB colonel and the United States of America.”

They also include Senate Homeland Security and Governmental Affairs Committee Chairman Ron Johnson (R-Wis.), who has been more deferential to the Trump administration when it comes to foreign policy and suggested he would be for expanding sanctions against Russia only “if you can get sanctions to work.”

“We recognize the complexity of our relationship and the numerous issues that the Administration needs to address with Russia. However, the murder of dissidents cannot be tolerated,” Johnson wrote in a letter to Tillerson penned this week with Sen. Chris Murphy (D-Conn.). “We ask that you make this issue a priority.”

Yet whether that alarm translates into enough votes to allow Congress to assert itself on Russia remains to be seen.

“Most people see Russia as deserving to be punished for interfering in our election, and to not punish Russia for interfering in our election would be the worst possible signal to send,” Graham told reporters Tuesday. “If they don’t pay a price, they’re not going to stop.”