In the wake of many of his supporters and progressives openly questioning the cognitive capabilities of former Vice President Joe Biden, Democratic presidential candidate Sen. Bernie Sanders (I-VT) said on Sunday that he doesn’t make “personal attacks” on Biden while waving off concerns that the ex-veep isn’t “up to the task” of being president.

Appearing on CNN’s State of the Union, the democratic-socialist Vermont senator was asked by anchor Jake Tapper about tweets his campaign staff sent over the weekend comparing Sanders’ robust campaigning to Biden’s lighter schedule.

“Bernie has three public events just today in two different states, each speaking engagement extending for close to an hour,” Sanders campaign manager Faiz Shakir tweeted in response to a report that Biden spoke for just seven minutes at a Saturday rally in St. Louis.

“Do you think that Vice President Biden is not up to the task in terms of the rigors of being either the Democratic nominee or being the president?” Tapper wondered aloud.

“No,” Sanders responded. “No, I think what we’re talking about is my schedule, which I just mentioned to you. By the way, we’re in Grand Rapids, Michigan, and later this afternoon we’ll hold a rally here.”

After noting that Rev. Jesse Jackson would be joining him on the trail and supporting his campaign, Sanders pointed out that he wouldn’t be taking personal shots at his Democratic primary rival.

“But look, Joe Biden is a friend of mine and Joe and I have disagreements on the issues,” Sanders added. “I do not make personal attacks on Joe.”

Earlier in the interview, Sanders also said that while he was the best candidate to win over Midwestern voters, such as in Michigan, he also felt that Biden could defeat Trump if the ex-veep became the nominee.

"I’ve been asked a million times and I believe Joe can beat Trump," Sanders said. "I believe if Joe is the candidate, I’ll do everything I can to ensure that he does."

In the wake of Biden leapfrogging Sanders as the Democratic frontrunner, many of the former vice president’s critics on the left have openly begun suggesting that the 77-year-old candidate is suffering from cognitive decline.

“After disappearing for the week, this isn't a convincing response to growing concerns—first implied in the debates by Julian Castro, then raised by Cory Booker, today reported in @Politico—about Biden's cognitive decline,” The Intercept’s Glenn Greenwald tweeted on Saturday. “Soon he'll just appear by hologram, spouting phrases.”