Trump tells top Democrat impeachment 'subverting America's democracy'

President Donald Trump on Tuesday told the opposition Democrats' leader in Congress that impeachment is an attempted "coup" that is "subverting America's democracy."

In an extraordinarily angry letter stretching more than five pages, Trump told Nancy Pelosi, speaker of the House of Representatives, that "history will judge you harshly."

Referring to a famous miscarriage of justice in 17th century US history, Trump said he'd been given less rights than "those accused in the Salem Witch Trials."

The Democratic-led House is expected to impeach Trump for abuse of office in a vote on Wednesday. He is accused of attempting to use his power to force Ukraine into opening what would have been a damaging probe of one of his main 2020 reelection rivals, Joe Biden.

He is also accused of obstructing Congress by refusing to cooperate with the impeachment probe, barring staff from testifying and holding back documentary evidence.

In remarks to reporters in the Oval Office, Trump rejected that he'd done anything wrong.

"It's a total sham," he said.

Asked if he took any responsibility for the crisis, he said: "I don't take any, zero to put it mildly."

In the letter, which ended with Trump's usual over-sized signature in thick black pen, he accused Pelosi of being the culprit.

"You are the ones interfering in America's elections. You are the ones subverting America's Democracy. You are the ones Obstructing Justice. You are the ones bringing pain and suffering to our Republic for your own selfish personal, political, and partisan gain," he wrote.

"This is nothing more than an illegal, partisan attempted coup that will, based on recent sentiment, badly fail at the voting booth," he wrote.