The first day of the impeachment trial of President Donald Trump has begun with battle over its format.

 This is the third such trial in US history.

So far the senators have debated the rules under which the trial should be conducted. No witnesses have yet been authorized to testify.

Despite efforts by Democrats to force the White House to provide documents, the vote failed after splitting along party lines.

Republican Senate leader Mitch McConnell, who sets the rules for the chamber, said he is hoping the trial will last just 10 days.

He made some last-minute changes to his proposal for how the Senate will conduct President Trump’s impeachment trial. The House managers and the president’s defense team now have three days each, instead of two, to present their opening arguments (although each side’s total time is still capped at 24 hours).

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Mitch McConnell has also changed the rules of evidence somewhat, allowing the House managers to introduce material gathered during their hearings unless a majority of the Senate objects.

He has said he had the Republican votes he needed to pass his rules package, but perhaps he felt some pressure from within his own ranks to more closely align his proposal to the way President Bill Clinton’s impeachment trial was run in 1998.

However, Democrats will still be calling for more. They want a guarantee of witnesses, something that doesn’t seem likely to happen.

Democrat Charles Schumer said a trial without witnesses or evidence would be “a cover-up”.

President Trump is accused of seeking help from Ukraine to get himself re-elected, and of obstructing Congress.

He has called the investigation a “hoax” and a “witch-hunt”.

Donald Trump is only the third president to face an impeachment trial.