Washington: US President Donald Trump is trying to provoke the Democrats to impeach him as he wants to "solidify" his base ahead of the 2020 election, said House Speaker Nancy Pelosi on Tuesday.

"Trump is goading us to impeach him. That's what he's doing. Every single day, he's just like, taunting, taunting and taunting, just because he knows that it would be very divisive in the country. But he doesn't really care. He just wants to solidify his base," The Hill quoted Pelosi as saying while speaking in an event.

Pelosi made the comments after Treasury Secretary Steven Mnuchin had turned down a request by the House Democrats' to make Trump's personal tax returns public.

"I am informing you now that the Department may not lawfully fulfil the Committee's request," Mnuchin wrote in his one-page letter on Monday.

The letter came after Mnuchin missed two deadlines in the last month to divulge tax details.

Mnuchin had said that the request by the Democrats is "unprecedented" arguing that it raises "serious constitutional questions" that could have "dire consequences" for taxpayer privacy.

After becoming a presidential candidate in 2016, Trump has refused to release any details of his tax returns.

This prompted the Democrats to knock the doors of Treasury Department, demanding it to divulge Trump's tax information, suspecting that there could be some evidence of possible wrongdoings by the 72-year-old leader.

Meanwhile, Trump contradicted Attorney General William Barr's statement last week that Special Counsel Robert Mueller "should not testify" on his investigation into alleged Russian collusion in 2016 presidential polls.

While Mueller found no Russian collusion in Trump's campaign for 2016 presidential elections during his 22-month long investigation, he fell short of completely exonerating the incumbent US President when it came to obstruction of justice, Barr had said while releasing the redacted report last month.

US House Judiciary Committee Chairman Jerrold Nadler has scheduled a vote for Wednesday (May 8) to hold Barr in contempt of Congress after the latter failed to adhere to a deadline to furnish Mueller's full and unredacted report on alleged Russian collusion in 2016 presidential election.

The contempt vote is scheduled to be held at 10 am (local time).