Donald Trump has accused senior Democrats of deliberately timing his impeachment trial to wreck the chances of Bernie Sanders becoming their party's presidential nominee.

Iowa is the first state to vote in the Democrat race on Feb 3, but Mr Sanders will be unable to campaign there because, as a US senator, he will be required to be a juror in the trial in Washington.

Mr Sanders will have to sit in silence, for six days a week while the hearing proceeds.

In 2016 the hierarchy of the Democratic party faced accusations that it deliberately sought to influence the nomination process in favour of Hillary Clinton amid fears that Mr Sanders, a democratic socialist, was too radical.

Floating his own conspiracy theory, Mr Trump said: "They are rigging the election again against Bernie Sanders, just like last time, only even more obviously.

"They are bringing him out of so important Iowa in order that, as a Senator, he sit through the Impeachment Hoax Trial."