Two contentious Americans are facing off. 

In one corner: the creator of a hit HBO show. In the other: a billionaire businessman running for president.

Lena Dunham, a Hillary Clinton supporter, said she'd move to Canada if Donald Trump is elected president. The Republican frontrunner responded by calling Dunham a "B-actor" who "has no, you know, mojo."

Dunham made her comment in an interview with Andy Cohen at the Matrix Awards on Monday, according to The Hollywood Reporter. Trump was then asked about it in a phone interview on "Fox and Friends" on Tuesday.

When the Fox anchors started listing the names of other celebrities, including Whoopi Goldberg and Rosie O'Donnell, who said they'd move to Canada if he were elected, Trump said he would "immediately get off this call and start campaigning."

"Well now I have to get elected, now I have to get elected because I'll be doing a great service to our country," he said.