The 100 senators will hear four hours of closing arguments split equally between Trump’s legal team and prosecutors from the Democratic-controlled House of Representatives, which charged him with abusing power by pressuring Ukraine to probe political rival Joe Biden, and then obstructing their inquiry.
The Republican-run Senate voted on Friday not to hear from witnesses including Trump’s former national security adviser John Bolton, despite a strong push by Democrats and opinion polls showing most Americans wanted to hear from them.
When the arguments are complete, the senators will be able to make speeches until Wednesday when a final vote will be taken at 4 p.m. EST (2100 GMT) to determine whether Trump is guilty of the charges and should be removed from office.
Trump will deliver his annual State of the Union speech to a joint session of Congress on Tuesday night. Republicans had been pushing for a final vote on impeachment last weekend so that he could use the speech to reset his agenda. But late last Friday that timetable was upended for reasons that were not immediately clear, and the vote was pushed to Wednesday.