US President Donald Trump has demanded an immediate impeachment trial in the Senate, amid an impasse among Democrats and Republicans over when it may start.
On Wednesday, the House impeached Mr Trump on charges of abuse of power and obstruction of Congress.
But Democrats have refused to start the proceedings, arguing the Republican-controlled Senate is refusing witnesses and will not hold a fair trial.
The Senate's numbers mean Mr Trump is almost certain to be acquitted.
The impeachment process has been highly toxic and divided almost totally along party lines.
The two charges agreed on Wednesday follow accusations that Mr Trump pressured Ukraine to dig up damaging information on Democratic rival Joe Biden and his son Hunter, and then refused to co-operate with a congressional inquiry into the matter.
In a series of tweets, the president accused the Democrats of not wanting to go to trial because their "case is so bad".
He tweeted: "So after the Democrats gave me no Due Process in the House, no lawyers, no witnesses, no nothing, they now want to tell the Senate how to run their trial. Actually, they have zero proof of anything, they will never even show up. They want out. I want an immediate trial!"