With a megaphone, Biden addressed members of the United Auto Workers union with a hat on the organization, recalling the "sacrifices" they made to "save the industry" during the 2008 crisis.

The US president said workers deserved a "significant raise".

Biden is the first sitting U.S. president to head to a sit-in site.

The presidential support in an ongoing social dispute between the United Auto Workers union and the Big Three companies — General Motors, Ford and Stellantis — is a reminder of the close ties Biden has forged during his political career with trade unions.

It also highlights the importance of Michigan, as the Democratic president seeks a second term in the 2024 election in which he could face his opponent in the last election, former President Donald Trump.

Michigan is the central state of an unprecedented strike movement affecting the three largest U.S. sector companies.

"Very proud"

Before Biden's arrival, dozens of striking workers outside a factory in Wayne had staged a sit-in, holding banners demanding "saving the American dream" and setting a fire near a tent.

Patrick Smaller, a participant in the strike, told AFP: "It's a huge event, it's a big support because he believes in the cause we are fighting for, it makes me very proud."

After meeting the protesters at the Ford plant, Biden went to meet strikers in front of a General Motor plant in Belleville, located nearby, where workers were waiting for him.

"I hope his coming and his support will help us," said Kristy Komitski, 44, nine of whom have been spent working at the plant, stressing that this "shows companies that we have the support of the president and with a little luck they will quickly accept a deal."

Curtis Cranford, 66, who says he is a Republican voter "because of immigration and abortion," stressed that "taking a public stand and declaring support for our cause is very important."

With his solidarity vigil on Tuesday, Biden is seeking to steal the spotlight from his Republican rival, who plans to head to the same state on Wednesday to get closer to the workers he is building his hopes on in order to regain the White House.

This is enough to make this historic strike the subject of a political battle.

Trump, who announced his trip before Biden announced a similar move, had accused the Democratic president of imitating him. His spokesman Jason Miller described Joe Biden's visit as "nothing more than a bad photo shoot."

Pro-union

For Biden, the challenge is to prove that he is the head of the working classes, the advocate of unions, and the architect of the United States' industrial renewal.

But the octogenarian, whose popularity is declining and his physical condition is focused on every trip, is walking a minefield as the current demand move could be extremely devastating to the U.S. economy.

The strike at automakers General Motors and Stellantis was widened by a lack of progress in union negotiations, unlike Ford, where "real progress" was made.

Biden has repeatedly stressed that manufacturers must distribute their "record profits" to their workers.

Asked whether the president was biased in social conflict, the White House spokeswoman preferred to avoid answering, stressing that Joe Biden wanted above all to reach an agreement that "takes into account the interests of both sides."

"We do not interfere in negotiations."

"He wants to take your jobs"

Joe Biden made his support for unions a hallmark of his tenure, and United Auto Workers' support for his 2020 nomination helped Michigan swing in his favor, while the state voted for Donald Trump in 2016.

However, the Democratic president's government's policy is one of the reasons behind the historic turmoil in the automotive industry, as it pushes for more green vehicles.

Donald Trump said on Truth Social, "When he walks slowly to pretend he's at a sit-in, remember he wants to take your jobs and send them to China."

Subsidies for electric cars in Biden's grand climate plan are limited to U.S.-made cars.

The Republican's hopes of returning to the White House are largely based on the Labour votes he won in 2016 in key states such as Michigan, Pennsylvania and Wisconsin.

Donald Trump will speak Wednesday at a parts manufacturing plant in Clinton, Michigan, according to his campaign team, just over 60 kilometers from where Biden visited.