Democratic presidential candidate Bernie SandersBernie SandersTop Democratic super PACs team up to boost Biden Poll: Biden leads Sanders by 22 points GE employees urge company to use laid-off workers to make ventilators 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 TrumpDonald John TrumpCuomo grilled by brother about running for president: 'No. no' Maxine Waters unleashes over Trump COVID-19 response: 'Stop congratulating yourself! You're a failure' Meadows resigns from Congress, heads to White House 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 ClintonHillary Diane Rodham ClintonJuan Williams: Mueller, one year on Biden tops Trump by 9 points in Fox News poll With VP pick, Biden can't play small ball in a long ball world 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.