President Donald Trump on Thursday denied being embarrassed by Russian President Vladimir Putin in a 2017 G20 meeting, as alleged by his former secretary of state, Rex Tillerson.

Trump called Tillerson "dumb as a rock" and "totally ill prepared and ill equipped to be Secretary of State," even though he supported Tillerson through a Senate confirmation and hired him personally.

Trump had previously sparred with Tillerson over who is more intelligent.

President Donald Trump on Thursday responded to a story that he had been embarrassed by Russian President Vladimir Putin by denying it. He also said the source of the story — Rex Tillerson, whom he hired and saw through Senate confirmation as his first secretary of state — is "dumb as a rock."

Tillerson said that at the 2017 G-20 meeting in Hamburg, Germany, where Trump and Putin first met, the Russian leader was much better prepared and ran circles around the Trump, The Washington Post reported on Wednesday.

Tillerson's comments came from a seven-hour-long closed-door testimony before the House Foreign Affairs Committee on Tuesday, according to the Post.

The Trump-Putin exchange was reportedly expected to last 45 minutes, but ran for more than two hours as the Russian president asserted himself on matters of global significance, according to Tillerson.

"We spent a lot of time in the conversation talking about how Putin seized every opportunity to push what he wanted," one committee aide told The Post. "There was a discrepancy in preparation and it created an unequal footing."

Trump initially denied being ill-prepared, but on Thursday dialed up the strength of his response by attacking Tillerson's intelligence.

"Rex Tillerson, a man who is 'dumb as a rock' and totally ill prepared and ill equipped to be Secretary of State, made up a story (he got fired) that I was out-prepared by Vladimir Putin at a meeting in Hamburg, Germany. I don't think Putin would agree. Look how the U.S. is doing!" Trump tweeted.

Trump had previously sparred with Tillerson over who is more intelligent. Tillerson, after a fraught policy meeting, reportedly once called Trump a "moron," which he later denied.

After the "moron" story broke on NBC, Tillerson held a press conference in which he specifically said that Trump is smart.

Read more: Tillerson dismisses reports that he considered resigning, says Trump is 'smart' but doesn't deny calling him a 'moron'

Later, Trump would challenge Tillerson to an IQ test, asserting that he would win.

However, before Trump nominated Tillerson, the president praised him as a "world-class player and dealmaker."

Trump's interactions with Putin have come under extreme scrutiny as multiple investigations sought to figure out the extent of his campaign's connection to Russian influence.