Republican Senator Lamar Alexander of Tennessee will oppose calling more witnesses in Donald Trump’s impeachment trial, all but dashing Democratic efforts to hear more testimony and boosting odds the Senate will vote to acquit Trump as early as Friday.

A vote on witnesses, expected on Friday, could lead to an abrupt end and assured acquittal in only the third presidential impeachment trial in American history.

Trump was pressing for action in time for his State of the Union address, and that now seems likely. As the Senate adjourned late on Thursday, it set the date for Tuesday night’s speech. Despite the Democrats’ singular, sometimes-passionate focus on witnesses after revelations from John Bolton, the former national security adviser, the numbers are now falling short. It would take four Republicans to break with the 53-seat majority and join with all Democrats to demand more testimony.

Alexander said in a statement there was “no need for more evidence,” giving the Trump team the likelihood of a Senate vote in its direction.

Trump was impeached by House last month on charges that he abused his power jeopardising Ukraine and US-Ukraine relations.

Before Alexander’s statement, Republican Sen Susan Collins of Maine said late Thursday she would vote to allow witnesses, briefly raising Democrats’ hopes for a breakthrough.

Collins, Alexander and Lisa Murkowski of Alaska were playing an outsized role in the final hours of debate with pointed questions. Another Republican senator, Mitt Romneyhas made clear he will vote for witnesses.