WATCH: CNN's Jake Tapper mocked Donald Trump for 'knowing a lot about a meeting he said he didn't know about'

On Monday, CNN's Jake Tapper slammed President Donald Trump for putting himself in a lying knot over the Trump tower meeting.

"Sure seems like President Trump knows a lot about a meeting he says he didn't know much about," Tapper said. "The president changing his story on the Trump Tower meeting once again."

President Trump tweeted that the purpose of the Trump tower meeting was only to get dirt on Hillary Clinton.

"President Trump yet again changing the entire story surrounding the now infamous 2016 Trump Tower meeting admitting for the first time the only reason for the meeting was to get dirt on Hillary Clinton.

Taper said that President Trump's tweets are a sign that he is worried about  special counsel Robert Mueller's Russia investigation.

"In response to a story in The Washington Post and another of which sources close to the White House told Kaitlin Collins that President Trump is increasingly worried of whether his son Donald Trump Jr. might be legally exposed in the special counsel's Russia investigation," Tapper said.

Watch the video below via CNN.