Indicted US Representative George Santos on Thursday struck a defiant note ahead of an expected vote to expel him from Congress and lashed out at other lawmakers in what could be his final days on Capitol Hill.

"This is bullying," Santos said at a news conference outside the Capitol. "It's all theatre."

The 35-year-old first-term congressman faces criminal campaign-finance charges and has admitted to fabricating much of his biography. His fellow Republicans have scheduled a vote on his expulsion on Friday.

Santos survived one expulsion vote earlier this month, but faces longer odds this time. A bipartisan congressional probe released after the vote found evidence that he spent campaign money on Botox, luxury brands such as Hermes and on OnlyFans, an online platform known for sexual content.

That has prompted some of the Republicans who previously voted against removing him to withdraw their support.

Santos declined to comment on that report, but said he was not wearing anything purchased with campaign funds.

"These are six years old," he said, pointing at his shoes.

Later in the day, he filed a motion to force an expulsion vote against Democratic Representative Jamaal Bowman, who pleaded guilty in October to a misdemeanour charge of setting off a fire alarm before a vote. That is unlikely to succeed as it would need substantial Democratic support.

"This is just another meaningless stunt in his long history of cons, antics, and outright fraud," Bowman said in a statement.

Santos has said he will not run for reelection next year but has remained bellicose in the face of growing pressure that he step down. The drumbeat of scandal has left him isolated in Congress, where he sits on no committees and has little influence.

Santos predicted he would be forced out in Friday's vote and said he was proud of his record in Congress. "I wish I could do more, (but) if this is it, this is it," he said.

Without his seat, Republicans' already slim 222-213 majority would narrow further. His district, which includes parts of New York City and its Long Island suburbs, is seen as competitive.

An election to fill his seat would be held within three months, according to New York state law.

At least 77 Republicans will have to vote for expulsion, along with the chamber's 213 Democrats, to meet the two-thirds majority required under the US Constitution. (Reuters)