Tapper calls out Bernie: 'Are you truly doing everything you can do to defeat Donald Trump?'
CNN host Jake Tapper, Vermont Sen. Bernie Sanders -- (CNN screen grab)

Appearing on CNN's State of the Union on Sunday morning, Vermont Sen. Bernie Sanders was pressed by host Jake Tapper over his refusal to endorse rival Hillary Clinton, leading to questions about his support for the presumptive Democratic nominee over Donald Trump.

Sharing clips of Sanders earlier in the week admitting that "in all likelihood" he would be voting for Clinton in November, Tapper wondered if the candidate's "hestitation" was sending the wrong signal to his supporters.

"When your supporters hear you say 'in all likelihood,' your vote will go to Hillary Clinton, do you think they come away thinking that maybe you'll run as a third party candidate? Maybe it's not that important to you that she wins," Tapper asked. " I mean, there's a hesitation there."

"Media focuses on politics as a game," Sanders replied. "What we are talking about and what this whole campaign is about is transforming the United States. Dealing with the issues that led to Brexit. Understanding why the middle class continues to decline," adding that he is trying to "build a strong progressive political movement that takes on big money interests."

"With all due respect, Senator, I'm not viewing this as a game," Tapper replied. "I'm looking at the fact that I talk to your supporters all the time and many of them do not want to vote for Hillary Clinton, and they feel very negatively towards her. And if it is important to you, as you say it is, to defeat Donald Trump, I wonder if you are truly doing everything you can do to defeat Donald Trump."

"I am going to do everything that I can do to defeat Donald Trump," Sanders shot back. "But a lot of that responsibility, about winning the American people over to her side, is going to rest with Secretary Clinton. Is she going to address the issues -- we got something like 12 or 13 million votes."

Watch the video below via YouTube: