President Donald Trump's moves in recent weeks to ease economic pressure on Russia while stepping up criticism of Ukraine have triggered bipartisan opposition in Congress, potentially complicating his agenda after next month's midterm elections.

Seeking to draw Russian President Vladimir Putin into negotiations to end the war in Ukraine, Trump has lifted sanctions on Russian diesel exports and waived newly enacted sanctions against Russian officials, oligarchs, banks and state enterprises.

At the same time, he has increased pressure on Ukrainian President Volodymyr Zelenskiy, calling for him to be replaced as the country's leader. A satellite system used by Ukraine for battlefield communications and drone operations was throttled following an order from inside the White House, Reuters reported last week.

Seventeen Democrats and five Republicans in the House of Representatives urged Trump in an October 15 letter to "apply the Graham law's sanctions to their fullest extent and without delay." The lawmakers added that Putin "has repeatedly shown that he responds to pressure, not goodwill." They were referring to legislation, championed by the late Senator Lindsey Graham of South Carolina, that Congress passed overwhelmingly and Trump signed into law in mid-September.

The Republican signatories were Representatives Brian Fitzpatrick of Pennsylvania, Joe Wilson of South Carolina, Michael McCaul of Texas, Don Bacon of Nebraska and Dan Newhouse of Washington state.

The backlash could pose new hurdles for Trump after the November 3 midterm elections, when Congress takes up defense and spending bills that lawmakers could use to try to reverse or alter his Russia policies.

Fitzpatrick went further. In a post on X on Monday he wrote that any move to limit the use of "Starshield" intelligence to warn Kyiv of Russian attacks would be "fully investigated" by Congress with "harsh and punitive budget cuts to any responsible agency or agency head." The White House pushed back in an email to Reuters:

“President Trump has been clear that he wants to see this brutal war come to an end," White House spokeswoman Taylor Rogers said, adding that Trump "retains the ability to exercise these authorities at any time if he determines that doing so would advance national interests." The pushback has raised the possibility that some Republican lawmakers could join Democrats in investigations and legislation reversing Trump's priorities following the midterm elections.

Congress' post-election work includes attempts to pass a bill authorizing defense programs for another year and across-the-board government spending through September 30, 2027, that includes appropriations for the Pentagon and intelligence agencies.

If Congress uses those bills to try to change his Russia policies, Trump could veto them, setting up a showdown.

James Lindsay, a US foreign policy expert at the Council on Foreign Relations, said the Republican backlash was not surprising given the Senate's bipartisan votes on the Graham bill. But passing legislation faces major challenges, Lindsay said.

"Even if Congress can overcome its institutional divisions, its partisan divisions and overcome a presidential veto ... that's no guarantee the president will act or observe that constraint," he said. Despite the growing pushback, many Republicans are backing Trump.

Republican Senator Ted Budd told Reuters at a Trump rally in his home state of North Carolina that he supports the president's pivot toward Putin, saying the recent agreement on Russian diesel sales was important to keep Moscow involved in negotiations to end its war with Ukraine.

"It's a very minimal dollar amount actually to Russia, but it's enough of a fig leaf to get them to the table to bring an end to the aggression against Ukraine," said Budd, an Armed Services Committee member.

The elections, which will determine whether Republicans hold their narrow House and Senate majorities, could influence the way legislative battles between the two parties, and with Trump, turn out.

Trump is not on the ballot, but the elections are widely seen as a referendum on his presidency. Voters are on edge over rising consumer prices and the war with Iran.

An October 13 letter to Trump signed by five senior Senate Republicans, along with six Democrats, also criticized his diesel agreement.

House Speaker Mike Johnson, a staunch supporter of Trump, has even hinted at his discomfort with current Russia policy.

Asked on Fox News' Sunday Morning Futures program whether he supported Trump's decision to waive the Russia sanctions, Johnson said: "Congress voted on this decisively." He added that he was in discussions with Republican members of the Foreign Affairs and Intelligence committees.

"We understand that Putin cannot be trusted," Johnson said and added that he told White House officials: "We need to talk about it and I think carefully consider the unintended consequences that may ensue" from putting the new Russia sanctions on hold.