Sen. Bernie SandersBernard (Bernie) SandersSenate to vote Monday on Trump's VA nominee Senate approves resolution warning Trump not to hand over US officials GOP leader blocks resolution backing intelligence community on Russia MORE (I-Vt.) called on Hillary ClintonHillary Diane Rodham ClintonProminent Putin critic: If Trump turns me over, I'm dead Dems unveil slate of measures to ratchet up pressure on Russia Trump tweets old video of Clinton talking up 'a strong Russia' MORE to stop arguing about the 2016 presidential election and help unite the progressive movement against President Trump, in an appearance on "The Late Show."

"We need her help to go forward. Let's not keep arguing about 2016. Let's get together, take on Trump's desire to divide us up, let's go forward with the progressive agenda," Sanders said. "Ask her if she'll do that." 

Sanders was discussing what host Stephen Colbert should ask Clinton when she makes her first late-night appearance since the election on Colbert's show later this month.

Clinton is set to appear on the show Sept. 19, a week after her upcoming book, "What Happened," hits the shelves, to discuss her 2016 campaign and the Trump administration. 

Earlier this week, Sanders responded to Clinton's accusation from her upcoming campaign memoir that the senator's attacks against her during the Democratic primary did "lasting damage" to her campaign."

"I understand, Secretary Clinton ran against the most unpopular candidate in the history of this country, and she lost. And she was upset about that and I understand that. But our job now is really not to go backwards, it is to go forwards," Sanders said. 

"I think it's a little bit silly to keeping talking about 2016," he added.