US Republicans have elected congresswoman Elise Stefanik, an outspoken defender of Donald Trump, as their new House conference chair, as the party scrambles to unify amid an explosive debate about its direction.

Ms Stefanik, a 36-year-old former moderate representing upstate New York, easily overcame a late entrant to the race and won strong support from the Republican conference in a closed-door vote of 134 to 46.

"My focus is on unity, because that's what the American people and that's what our voters deserve," she told reporters after vaulting into the number three House Republican position - becoming the party's most powerful woman in Congress.

"We are going on offence and are going to win back the majority in 2022" in the House of Representatives, said Ms Stefanik, the party's new top messenger.

Liz Cheney was ousted earlier this week from the leadership post

The vote came two days after the conference ousted Liz Cheney, a conservative stalwart and daughter of former vice president Dick Cheney, from the post over her repeated criticism of Mr Trump and her refusal to embrace his false claim that Democrats stole the 2020 election.

With Mr Trump retaining enormous influence, Republicans have been desperate to tamp down swelling discord within party ranks over its future.

Conservatives aim to craft a coherent message heading into next year's midterm elections, but some Republicans fear that failing to reject Mr Trump's rhetoric about voter fraud could hurt the party at the polls.

But Ms Stefanik made clear that Mr Trump and Trumpism will remain vital in the effort to turn back the "radical, far-left socialist agenda" of President Joe Biden and his Democrats.

"I support president Trump, voters support president Trump," Ms Stefanik said. "He is an important voice in our Republican Party and we look forward to working with him."

Mr Trump, whose grip on the party has tightened with Stefanik's elevation, congratulated her for the "overwhelming" win.

"The House GOP is united and the Make America Great Again movement is Strong!" the former president said.