The US Senate is hearing opening arguments in the impeachment trial of President Donald Trump in Washington DC.
After both sides present their arguments, senators will have a 16-hour question-and-answer session, followed by a four-hour debate.
All votes on future motions in the trial will require a simple majority; the final vote on whether to convict the president needs a two-thirds majority of 67.
During the 12-hour-long session, the Republican-controlled Senate blocked a series of Democratic amendments to the rules resolution.
Each of the 11 measures offered by Senate Democrats, which included calls for top administration officials to testify and additional documents to be subpoenaed, was thwarted in almost all instances by the same party-line vote of 53 to 47.