FACTBOX-Trump impeachment: What happens next?

Here is what to look out for next as the proceedings advance in U.S. President Donald Trump's impeachment trial in the Senate:

Starting Jan. 21 * The House has until noon EST (1700 GMT) to file a rebuttal brief to the White House trial brief that called for immediate dismissal of the House's two articles of impeachment.

* The trial resumes at 1 p.m. (1800 GMT) and is expected to continue six days a week, with the exception of Sundays. * A vote could be held as early as Jan. 21 on Senate Majority Leader Mitch McConnell's proposed rules governing the first phase of the trial, which would leave open the option of voting later on whether witnesses would testify and new evidence could be introduced.

* Democrats are expected to try to amend McConnell's rules to stipulate that witnesses must be called, possibly leading to extensive debate over the rules of the trial. * Once the rules have been adopted, Trump's lawyers could move to have the two articles of impeachment dismissed. The Senate is not expected to approve the immediate dismissal of charges of abusing the powers of his office and obstructing Congress' investigation.

* Also, once the rules have been adopted, Democratic House "managers" who form the prosecution team would begin to present their case against Trump. It could start on Jan. 22. When the House managers have finished, the president's team will respond with its opening arguments. During the arguments, senators sit as jurors and are not allowed to speak unless they are in a closed session. * Following the opening arguments, senators would be given 16 hours to submit questions to each side.

Late January to early February * Democrats is expected to continue pushing to hear from witnesses during the trial. If McConnell's resolution on initial trial rules is adopted, as expected, senators would likely vote sometime after the trial has started on whether to introduce witness testimony sought by the Democrats. If the Senate decides to subpoena witnesses, they would first be deposed privately and the Senate would then decide whether they should publicly testify.

* Votes to present final arguments could occur if no subpoenas are issued and if witnesses are not approved by a majority of the Senate. Feb. 4

* Trump is scheduled to deliver the annual State of the Union address to a joint session of Congress.