Bernie Sanders isn’t officially endorsing Hillary Clinton … yet.

The Vermont senator visited “The Late Show” on Thursday night, and was asked by CBS host Stephen Colbert if he’d endorse the presumptive Democratic presidential nominee.

Sanders’ response? A decisive “no.”

Also Read: Donald Trump Welcomes Bernie Sanders Supporters 'With Open Arms'

Sanders went on to blast the presumptive Republican presidential nominee, Donald Trump, who has been courting his supporters. When asked how they should vote, Sanders replied, “My supporters are smart enough to know that we do not want a bigot to become president of the United States,” prompting raucous applause.

“Secretary Clinton and I agree Trump has got to be defeated,” he added.

Sanders also revealed that his campaign has been “talking to” Hillary Clinton’s, specifically on the topic of public education. He added that he wants his supporters to have a presence at the upcoming Democratic National Convention.

Also Read: Cartoon Donald Trump Returns to 'Late Show' to Court Bernie Sanders Voters (Video)

The senator also showed off his signature sense of humor, smiling when Colbert said he needed to “kowtow to corporate interests,” just before taking a commercial break.

Watch the extended video above.

“The Late Show” airs at 11:35 p.m. on CBS.