A sweeping tax overhaul moved closer to passage as a pair of wavering Republicans said they would vote in favour.

Senators Marco Rubio and Bob Corker had both expressed reservations about the landmark legislation, but they said they were now on board.

Mr Corker, a Tennessee Republican who has feuded publicly with Donald Trump, said he would back the legislation despite concerns about the measure inflating the deficit. A Congressional Budget Office analysis of a version of the legislation found it would add some $1.4 trillion to the deficit, but supporters argue surging economic growth would offset that.

“I believe that this once-in-a-generation opportunity to make US businesses domestically more productive and internationally more competitive is one we should not miss,” Mr Corker said in a statement.

And Mr Rubio, who had balked at what he said was an overly skimpy child tax credit for people on the bottom of the income scale, said on Twitter that a measure making the credit more generous was “a solid step toward broader reforms which are both pro-growth and pro-worker".

Multiple outlets reported that Mr Rubio was prepared to vote for the bill. The backing from him and Mr Corker likely gives Republicans enough votes to advance the measure to Mr Trump’s desk.

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Both the Senate and the House have already passed tax plans and must now agree on a joint version. Republicans on Friday unveiled their bill, which would slash the corporate tax rate from 35 per cent to 21 per cent and lower the top rate for affluent individuals from 39.6 per cent to 37 per cent.

It would also jettison a requirement that Americans have health insurance, dismantling a key element of Barack Obama’s healthcare law after Republicans failed to advance bills specifically focused on repeal.