Sen. Bernie Sanders’ top campaign adviser says the front-runner will decline billionaire Democratic rival Mike Bloomberg’s offer to spend millions on his behalf if Sanders wins the party’s nomination.

“It’s a hard no,” Jeff Weaver, Sanders’ closest aide, told NBC News.

“Bernie has said he’s going to fund his presidential campaign with small-dollar contributions, and I think we can do that,” he added, “I think we can raise over a billion dollars in small-dollar contributions.”

Back in January, Bloomberg pledged to continue funding his massive campaign, which is comprised of over 2,000 staffers, through the general election in November — even if he loses the nomination. The former mayor said he would continue to employ all staffers and retain Hawkfish, the Bloomberg-founded digital company that’s behind the campaign’s ad blitz, until Election Day to financially support whichever candidate won the Democratic primary — even if that candidate was Sanders.

One exception to the pledge, however, was that Bloomberg would not spend on a candidate who rejected his offer.

In response to Weaver’s comments, Bloomberg senior adviser Howard Wolfson told the network, “Bernie said he didn’t want [Bloomberg’s] money, so we’re not going to. I don’t think it would be prudent to spend on behalf of somebody who didn’t want it.

“I think everyone else has said they want the help, including Elizabeth Warren. If Elizabeth Warren is the nominee, we will do everything we can to help her. Sanders is the one candidate who said he didn’t want the help,” Wolfson added.

Sanders said in an interview earlier this month that he had “a real problem” with Bloomberg spending hundreds of millions of his $65 billion net worth on his presidential bid.

“I don’t begrudge his wealth, but I do begrudge a billionaire thinking he can buy the election. He has every right in the world to run for office … But he doesn’t have the right to buy an election. This is exactly the problem with American politics,” the Democratic socialist said.

A spokesperson for Sen. Warren (D-Mass.), who was referenced by Wolfson, did not immediately respond to a request for comment by The Post regarding whether she would accept Bloomberg’s money.

Last week, former South Bend Mayor Pete Buttigieg said he would accept the fellow former mayor’s offer of financial help.

“Sure,” Buttigieg said during a CNN town hall of taking the mayor’s donation. “Look, right now, obviously I’m competing against Mayor Bloomberg. We have, I think, different approaches and different visions. But his philanthropy supported a million-dollar effort in our community to help low-income people get transportation to go to work. I’m not going to reject that help because it came from a very wealthy person.

“This is the moment to bring everybody that we can into this effort, and I promise exactly one thing in return for any contribution, which is we’re going to take that contribution and use it to go beat Donald Trump.”