Asked on MSNBC's Morning Joe whether he will vote for Clinton in November, Sanders responded "Yes."
The Vermont senator, who has not yet formally ended his 2016 campaign, said that stopping Donald Trump from becoming president must be an overarching goal.
"I think the issue right here is I'm gonna do everything I can to defeat Donald Trump," he said.
But Sanders also dismissed the idea that he should withdraw from the Democratic race now that Clinton has secured the nomination.
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"Why would I want to do that when I want to fight to make sure that we have the best platform that we possibly can, that we win the most delegates that we can?" he said.
And in a later interview on CBS, Sanders declined to formally endorse Clinton, although he indicated that he "hopes" to before the convention.
"I haven't heard her say the things that need to be said," he said.
Sanders also insisted that his continuing presence in the race is not causing disunity in the Democratic Party.
"You talk about disunity. I talk about involving the American people in the political process," he said.