WASHINGTON (REUTERS) - The White House unveiled its detailed legal defence as the Republican-controlled US Senate gears up to begin President Donald Trump's impeachment trial on Tuesday (Jan 21).

Trump, who is only the fourth of 45 American presidents to face the possibility of being ousted by impeachment, submitted his most detailed arguments to date for why he should remain in office.

Here are some of the highlights:

1. White House argues House Democrats have failed to identify an 'impeachable offence'

"House Democrats' novel theory of 'abuse of power' improperly supplants the standard of 'high Crimes and Misdemeanours' with a made-up theory that would permanently weaken the Presidency by effectively permitting impeachments based merely on policy disagreements."

"House Democrats' 'obstruction of Congress' claim is frivolous and dangerous. House Democrats propose removing the President from office because he asserted legal rights and privileges of the Executive Branch against defective subpoenas..."

"The President directed three of his most senior advisers not to comply with subpoenas seeking their testimony because they are immune from compelled testimony before Congress."

2. White House says impeachment inquiry was 'irredeemably flawed'

"The process that resulted in these Articles of Impeachment was flawed from the start. Since the founding of the Republic, the House has never launched an impeachment inquiry against a President without a vote of the full House authorising it."

"House Democrats concocted an unheard-of procedure that denied the President any semblance of fair process. The proceedings began with secret hearings in a basement bunker... The President was denied any right to participate."

"Chairman (Adam) Schiff's hearings were fatally defective for another reason - Schiff himself was instrumental in helping to create the story behind them."

"House Democrats resorted to these unprecedented procedures because the goal was never to get the truth. The goal was to impeach the President, no matter the facts."

3. White House says Democrats have presented 'no evidence to support their claims'

"House Democrats have falsely charged that the President supposedly conditioned military aid or a presidential meeting on Ukraine's announcing a specific investigation. Yet...House Democrats do not have a single witness who claims, based on direct knowledge, that the President ever actually imposed such a condition."

"The evidence shows that President Trump had legitimate concerns about corruption and burden-sharing with our allies - two consistent themes in his foreign policy."