WASHINGTON — Bernie Sanders is warning that if onetime rival Joe Biden doesn’t do more to promote his policies and reach out to Latino voters, the Democratic presidential nominee is at risk of falling short to President Trump this November.

Sanders, a self-described democratic socialist who left the primary race in the spring and has worked to shift Biden to the left on key issues, has made the warnings in public and private in recent days. Most recently, he went on MSNBC on Sunday to express concerns that Biden wasn’t speaking up enough about his economic proposals.

“I think Biden’s in an excellent position to win this election, but I think we have got to do more as a campaign than just go after Trump,” he said. “We also have to give people a reason to vote for Joe Biden. And Joe has some pretty strong positions on the economy, and I think we should be talking about that more than we have.”

Democratic presidential candidate Sen. Elizabeth Warren, D-Mass., Joe Biden and Sen. Bernie Sanders, I-Vt., during a Democratic presidential primary debate on Jan. 14 in Des Moines, Iowa. Sanders is warning that if Biden doesn’t do more to promote his policies and reach out to Latino voters he’s at risk of falling short to President Trump this November. Patrick Semansky/Associated Press

In a Friday interview with PBS, Sanders was more blunt: “Am I here to tell you absolutely, this is a slam dunk, no chance that he will lose? That is not what I’m saying,” the Vermont senator said.

His comments follow a week when Biden campaigned with union workers in Michigan and released a tax plan focused on boosting U.S. manufacturing by punishing businesses that take jobs overseas. Biden also emphasized his economic agenda and attacked Trump for his handling of the pandemic while the former vice president spent Labor Day with union workers in Pennsylvania.

Sanders used his MSNBC appearance to urge Biden to speak more about some of his kitchen-table economic policies: raising the minimum wage to $15 an hour, lowering prescription drug costs and expanding health insurance coverage.

Sanders said Biden’s policies are “a compromise” but that they were “pretty strong, progressive policies.”

He also encouraged Biden to focus more on Latino and young voters, groups that broadly supported Sanders during the primary. Biden has struggled to build enthusiasm among young voters, and some Democrats have expressed concerns about what they see as the campaign’s lack of outreach to Latino voters, which Sanders echoed on MSNBC.

“We got to reach out to the Latino community. You know, a lot of young people, you’ve got a lot of Latinos, African Americans who may not vote. They’re not gonna for Donald Trump, that’s for sure, but they may not vote at all,” Sanders said. “How do we bring them into the political process? How do we get them to vote?”

A Biden campaign adviser, Symone Sanders, was asked Sunday on ABC’s “This Week” whether the campaign would take Sanders’ advice.

“We know that we have work to do. And we have said from the beginning, and Vice President Biden has been very clear about this … that we are really working to earn every single vote in this country. And we want to earn the votes of the Latino and Hispanic community,” she said.

Sanders has campaigned for Biden, holding virtual rallies in seven states, including one this weekend in Michigan. It’s one of three states where Sanders warned Democrats should be “nervous” about their chances, along with Pennsylvania and Wisconsin.

“The enthusiasm is with Trump, not with Biden,” Sanders said.

In 2016, Trump’s unexpected victories n those three Rust Belt states, bolstered in part by his support among white working class voters, helped deliver him the White House. The Biden campaign has focused much of its early efforts on those three states, with Biden and running mate Kamala Harris visiting all three in recent weeks.

While Sanders made his concerns public in recent interviews, he also has expressed them in private to the Biden campaign, according to Faiz Shakir, Sanders’ former presidential campaign manager.

“He has been in direct contact with the Biden team and has urged them to put more emphasis on how they will raise wages, create millions of good paying jobs, lower the cost of prescription drugs and expand health care coverage,” Shakir said.

Shakir said Sanders “also thinks that a stronger outreach to young people, the Latino community and the progressive movement will be of real help to the campaign.”

Biden has adopted some of Sanders’ more liberal proposals, but the Democratic nominee has been careful to avoid some of progressives’ more contentious policy priorities, such as defunding the police and adopting a fully government-run healthcare system. His commitment to a more centrist campaign has frustrated some progressives, who warn that Biden’s careful campaign could turn off young and minority voters.

But Sanders expressed confidence that those in the progressive movement who may be disappointed by Biden’s policies would still be motivated by a desire to win the White House.

“I would hope that, while people will have strong disagreements with Biden – I do – for the moment, put that aside,” Sanders said on PBS. “That’s what, in a sense, coalition politics is about: You come together for a common goal. The goal is to defeat Trump.”