Donald Trump suffered the embarrassment of becoming only the third US president in history to be impeached in December, but a trial to decide whether he should be removed from office still lies ahead.

In what is set to be a blockbuster trial, the Senate's 100 members will debate whether Mr Trump's actions in the Ukraine scandal merit hit removal from office.

The proceedings are expected to begin in earnest on Tuesday and could last for several weeks. A lengthy trial would overshadow the Democratic presidential nomination race, with the first votes cast in Iowa on February 3.

The Senate will ultimately vote on the two articles of impeachment passed by the House - one charging him with abuse of power, the other with obstructing Congress.

Mr Trump has pushed back on the accusations against him and called for a speedy Senate vote to dismiss the case against him.

But a handful of Republican senators have broken rank to say a number of witnesses should be called to testify in the trial, leaving the time frame for the proceedings still in doubt.