DETROIT, MI -- Democratic presidential hopeful Bernie Sanders blamed “disastrous unfettered free trade policies” for causing the United States to transition from a “General Motors economy” to a “Wal-Mart economy,” citing the global retail chain’s status as the country’s top employer.

The Vermont senator hosted a conversation with Michigan union auto workers on the negative impact past trade deals have had on the economy before a Friday rally in Detroit. Sanders condemned Democratic primary rival and former Vice President Joe Biden for his role in supporting trade deals like the North American Free Trade Agreement and allowing good-paying jobs to leave Michigan communities.

“What these trade deals have done is decimate the working class of this country," Sanders said. “It’s not just the loss of jobs, it’s wages going down, it’s a race to the bottom ... I have done my best to oppose these disastrous trade deals. Joe Biden, on the other hand, has totally supported them."

Biden was among Democrats who voted for NAFTA as a U.S. senator and was also an advocate for the Obama-era Trans-Pacific Partnership. Sanders and President Donald Trump campaigned in 2016 on renegotiating trade deals to benefit blue-collar workers.

The Michigan-centered event comes as Sanders prepares for a primary election bout against Biden next Tuesday, March 10.

Sanders has worked to draw a distinction between himself and Biden as states with large numbers of workers in industrial and manufacturing industries begin to vote. Sanders visited United Auto Workers on the picket line outside last year during a month-long strike against General Motors.

Sanders convened a group of Michiganders who worked at General Motors factories in Flint and Saginaw. Both cities have seen a loss of manufacturing jobs in the last several decades.

Manufacturing jobs used to be the “gold standard” for Americans, Sanders said, but free trade agreements have allowed corporations to move factories across the border to take advantage of cheaper labor.

Sanders also criticized “right to work” legislation passed in states like Michigan, which prohibits employers from requiring union membership or payment of dues as a condition of employment.

“All of the new income and wealth are going to the people on top,” Sanders said. “Clearly what we need to do is create an economy that works for all of us, not just the CEOs of large corporations.”

Both candidates have touted their support among labor unions and blue-collar workers as evidence that they can take on President Donald Trump in the general election. Trump narrowly flipped Michigan and other formerly Democratic-leaning Midwest states in part by campaigning on promises to rewrite NAFTA.

Trump’s United States-Mexico-Canada Agreement gathered bipartisan support in Michigan and passed earlier this year to the applause of Republicans and Democrats seeking a modernized replacement to NAFTA.

Sanders stood alone during the January Democratic debate by declaring he would not support the USMCA, and later voted against it in the Senate. Sanders said he deal lacks important environmental protections, though he said it is an improvement over NAFTA.

The Sanders campaign released a statement criticizing Biden’s work to pass NAFTA after Trump launched a similar line of attack at a Fox News town hall this week. Trump said Biden showed poor judgment in “pushing” the trade deal as a U.S. senator.

“Joe Biden made a deal: NAFTA,” Trump said Thursday. “He approved it. He was pushing it. It’s the worst trade deal ever made. We’re terminating NAFTA. We have the USMCA.”

Bernie 2020 campaign manager Faiz Shakir said Trump will exploit Biden’s vulnerability on trade to win battleground states that could swing the general election. Shakir argued Sanders’ stance on NAFTA makes him a stronger candidate to face Trump in November.

Sanders and Biden are essentially the last candidates standing after the Democratic Party assembled a large and historically diverse field of competitors. Both campaigns are making a large push to sway voters in Michigan in the final days of the election, with a flurry of rallies and smaller events planned throughout the weekend.

The race has become more competitive after the departure of several other candidates this week. Elizabeth Warren has not put her support behind either of the remaining candidates, but Amy Klobuchar, Pete Buttigieg and Mike Bloomberg coalesced around Biden.

Biden appears to be riding a surge of momentum after gathering more delegates than Sanders on Super Tuesday earlier this week. Michigan Gov. Gretchen Whitmer and several other high-profile Democrats put their support behind Biden in the final days of the primary.

U.S. Rep. Tulsi Gabbard, D-Hawaii, is still running and visited Detroit this week, but is far behind the other two candidates in terms of delegates.

David Dulio, head of the political science department of Oakland University, said it’s not clear that Sanders has an advantage against Trump on trade. Both politicians have railed against the negative impact of NAFTA, but the replacement agreement is Trump’s signature policy achievement.

“I don’t know where Sanders goes with that,” Dulio said. “I mean if he comes in to rail against trade agreements, Trump can follow up with a tweet that says, ‘Sorry Bernie I already did that.’”

Read more on MLive:

A complete guide: How to see Joe Biden, Bernie Sanders campaign events in Michigan this weekend and Monday

The big question for Michigan Democrats: Is Biden or Sanders more likely to beat Trump?

Michigan Gov. Gretchen Whitmer endorses Biden, joining campaign as a national co-chair

What happens if I voted for someone who dropped out of Michigan’s presidential primary?

What Michigan voters need to know about absentee ballots for March 10 primary

January Democratic debate shows Sanders alone in opposing USMCA