Senators have voted to consider witnesses in the impeachment trial of former president Donald Trump.
Closing arguments were expected on Saturday with no witnesses being called.
But lead Democratic prosecutor Jamie Raskin of Maryland asked for a deposition of Republican Jaime Herrera Beutler over fresh information.
She has widely shared a conversation she had with House Republican leader Kevin McCarthy over Mr Trump’s actions on January 6 as a mob was rioting at the US Capitol over the presidential election results.
Mr Raskin said it was necessary to determine Mr Trump’s role in inciting the deadly riot.
There were 55 senators who voted to debate the motion to subpoena, including Republican Senator Lindsey Graham, who changed his vote in the middle of the count.
Mr Trump’s attorney Michael van der Veen baulked at the request, saying he would then call 100 witnesses, and that it was not necessary.
The nearly week-long trial has been delivering a grim and graphic narrative of the January 6 riot and its consequences for the nation in ways that senators, most of whom fled for their own safety that day, acknowledge they are still coming to terms with.
Acquittal is expected in the evenly divided Senate, a verdict that could heavily influence not only Mr Trump’s political future but that of the senators sworn to deliver impartial justice as jurors as they cast their votes.
Senate Republican leader Mitch McConnell will reportedly vote to acquit Mr Trump and his decision is likely to influence others weighing up their votes.
House prosecutors have argued that Mr Trump’s rallying cry to go to the Capitol and “fight like hell” for his presidency just as Congress was convening to certify Joe Biden’s election was part of an orchestrated pattern of violent rhetoric and false claims that unleashed the mob.
Five people died, including a rioter who was shot and a police officer.
Defence lawyers countered in a short three hours on Friday that Mr Trump’s words were not intended to incite violence and impeachment is a “witch hunt” designed to prevent him from serving in office again.
Mr Trump is the only president to be impeached twice, and the first to face trial charges after leaving office.
Unlike last year’s impeachment trial in the Ukraine affair – a complicated charge of corruption and obstruction over his attempts to have the foreign ally dig up dirt on then-rival Mr Biden – this one brought an emotional punch over the unexpected vulnerability of the nation’s tradition of peaceful elections.
