Democratic presidential candidate and Vermont Sen. Bernie Sanders on Sunday rebuked President Trump’s assertion that he is a "communist."

“Obviously I am not a communist,” Sanders told Chris Wallace on “Fox News Sunday,” adding that Trump “maybe doesn’t know the difference.”

Sanders has described himself as a "democratic socialist."

Sanders also said Trump was a “pathological liar” for suggesting that he got “married in Moscow.” Sanders said he was in Russia to participate in a sister city program. 

Sanders contends that Trump himself practices a form of socialism, saying that Trump received subsidies and tax breaks from the government to run his business empire. 

“The difference between my socialism and Trump’s socialism is I believe the government should help working families, not billionaires,” Sanders asserted.

Trump made the comments about Sanders last week in an interview with Fox News. 

“I think he is a communist. I think of communism when I think of Bernie. You can say socialist. Didn’t he get married in Moscow?” Trump told Fox News host Sean Hannity. 

Trump has frequently called Sanders “crazy Bernie” while at his rallies. He has also pushed theories that the Democratic National Committee had conspired against Sanders in the 2016 Democratic primary.

In leaked audio from a private conversation in 2018, Trump said that if Hillary Clinton had chosen Sanders as her running mate in the 2016 election, it would have been tougher to win the presidency. 

“I think Bernie as vice president would have been tougher,” Trump said. “You know, I got 20 percent of [the] Bernie vote, people don’t realize that, because of trade, because he’s a big trade guy. He basically says we’re getting screwed on trade, and he’s right.”

Sanders is one of the frontrunners for the 2020 Democratic nomination and has been surging in the polls in recent weeks. The Sanders campaign managed to raise a massive $25 million in donations in January alone.