Lawyers for former U.S. President Donald Trump on Monday urged Senate to dismiss his impeachment case, terming the process a "selfish" plot by Democrats.

In a brief seen by the AP, the lawyers accuse the House Speaker of using the impeachment case for her own political gain.

"…this was only ever a selfish attempt by Democratic leadership in the House to prey upon the feelings of horror and confusion that fell upon all Americans across the entire political spectrum upon seeing the destruction at the Capitol on Jan. 6 by a few hundred people," the lawyers wrote in the brief.

"Instead of acting to heal the nation, or at the very least focusing on prosecuting the lawbreakers who stormed the Capitol, the Speaker of the House and her allies have tried to callously harness the chaos of the moment for their own political gain," they added.

The U.S. House of Representatives delivered an article of impeachment against former Trump to the Senate on 25 January, formally charging him with inciting an insurrection at the Capitol.

His lawyers also argue that the Senate is not entitled to try Trump now that he has left office.

The trial is scheduled to begin on Tuesday with a debate and vote on whether it's constitutional to prosecute the former president.