President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE argued Saturday that Democrats in Congress have launched another "Witch Hunt" against him amid backlash over reports that he urged Ukraine's president to launch an investigation into former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE.

In a tweet Saturday afternoon, the president asserted that Democrats were attempting to shield Biden from an investigation by going after Trump on the topic of Ukraine. Biden is currently leading polls for the Democratic presidential nomination.

Trump sent the tweet and others earlier Saturday pushing back a day after The Wall Street Journal reported that the president urged Ukraine's leader to investigate Biden's past dealings in the country.

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"Now that the Democrats and the Fake News Media have gone 'bust' on every other of their Witch Hunt schemes, they are trying to start one just as ridiculous as the others, call it the Ukraine Witch Hunt, while at the same time trying to protect Sleepy Joe Biden," he tweeted, adding, "Will fail again!"

Now that the Democrats and the Fake News Media have gone “bust” on every other of their Witch Hunt schemes, they are trying to start one just as ridiculous as the others, call it the Ukraine Witch Hunt, while at the same time trying to protect Sleepy Joe Biden. Will fail again! — Donald J. Trump (@realDonaldTrump) September 21, 2019

The latest charge from Trump comes as the president has for days defended his conversations with Ukrainian President Volodymyr Zelensky in the face of news reports about a whistleblower complaint detailing a supposedly troubling promise Trump made to a world leader during a conversation.

On Friday, Trump told reporters at the White House that the topic of his conversation with Ukraine's leader was unimportant, adding that his conversations with world leaders were "always appropriate."

"It doesn't matter what I discussed, but I'll tell you this: Somebody ought to look into Joe Biden's statement," he said.

Trump and his allies have labeled the unidentified whistleblower a partisan operative and have argued that none of the president's conversations about Ukraine or the former vice president's actions are improper.

Republicans have sought to prove that Biden pushed for the dismissal of a Ukrainian prosecutor who was investigating a company where Biden's son Hunter Biden served as a board member. The prosecutor ultimately resigned under a slew of corruption allegations.

In tweets and videos posted to social media this week, the president argued that Biden's involvement in the prosecutor's dismissal was "the real and only story" and a "disaster" for the former vice president.

"The Fake News Media and their partner, the Democrat Party, want to stay as far away as possible from the Joe Biden demand that the Ukrainian Government fire a prosecutor who was investigating his son, or they won’t get a very large amount of U.S. money, so they fabricate a story about me and a perfectly fine and routine conversation I had with the new President of the Ukraine," he tweeted earlier Saturday.

"Nothing was said that was in any way wrong, but Biden’s demand, on the other hand, was a complete and total disaster. The Fake News knows this but doesn’t want to report!" Trump added Saturday.

Earlier this week, Trump's personal attorney Rudy Giuliani Rudy GiulianiThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting CIA found Putin 'probably directing' campaign against Biden: report Democrats fear Russia interference could spoil bid to retake Senate MORE also acknowledged during a heated interview on CNN that he had urged Ukraine to investigate Biden.