Democratic presidential candidate Bernie Sanders Bernie SandersKenosha will be a good bellwether in 2020 Biden's fiscal program: What is the likely market impact? McConnell accuses Democrats of sowing division by 'downplaying progress' on election security MORE said he's still fighting to secure the nomination, though he noted it will be an uphill battle.

"It's difficult; it's not impossible," he said on CBS's "Face The Nation" on Sunday.

He'll need to win 65 percent of the delegates in the remaining contests to win the nomination.

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"Now 65 percent is a pretty heavy climb, but these are states ... that I think we're going to do very, very well in," the Vermont senator said.

Sanders also said he thinks he can garner support from superdelegates in states where he has won the majority of the vote.

He also called on voters to look at who the stronger candidate to beat Republican presidential front-runner Donald Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE in a general election would be.

"We appeal to not only the overwhelming majority of Democrats," he said. "We appeal to independents as well."

He said he is "absolutely" still fighting to beat Democratic front-runner Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE for the nomination.

"It's a tough fight," he acknowledged, though he touted his campaign's ideas as the future of the Democratic Party.