The US House of Representatives is set to vote on how the impeachment inquiry into President Donald Trump should proceed.
The resolution to be voted on sets out a more public phase of the process and is not a ballot on whether or not to impeach the president.
The measure also sets out the rights Mr Trump’s lawyers would have.
This will be the first formal test of support for the inquiry in the Democratic-controlled House.
President Trump is accused of trying to pressure Ukraine into investigating unsubstantiated corruption claims against his political rival, Joe Biden, and his son who worked with Ukrainian gas company Burisma.
Mr Trump denies wrongdoing and calls the impeachment inquiry a “witch hunt”.
Republicans have criticised Democrats for the closed hearings up to this point, in which Republican lawmakers have also taken part. But Democrats insist they were needed to gather evidence ahead of the public stage of the inquiry, and deny allegations they have been secretive.
The debate is expected to start at 09:00 (13:00 GMT). Democrats, who have 224 of the 435 seats in the House, need a simple majority to approve the resolution.
Earlier this week, Democrats in the House released an eight-page document setting out a two-stage process for the next phase of the inquiry.
In the first stage, the House Intelligence Committee would continue its investigations and hold public hearings. It would have the right to make public transcripts of depositions taken in private.
In the second stage, a public report on the findings would be sent to the House Judiciary Committee which would conduct its own proceedings and report on “such resolutions, articles of impeachment, or other recommendations as it deems proper”.