Thousands of members of the United Auto Workers union have gone on strike in the US. It is the first time that employees at Ford, General Motors and Chrysler's parent, Stellantis -- the so-called Big 3 -- have walked off their jobs together.

The workers began the strike after their current contract expired at 11:59 p.m. Thursday.

The union's president, Shawn Fain, described the situation as a "shame." He said the companies are not taking care of their workers despite referring to them as "family."

Union leaders are demanding a 36 percent wage increase over the next four years. They say the companies can afford it because they are enjoying record profits. The automakers have offered only a smaller raise.

The union has more than 140,000 members working at the Big 3, and not all of them are on strike. But if they do all walk out, analysts say, it could result in an economic loss of more than 5 billion dollars after only 10 days.

US President Joe Biden said he has been in touch with both sides. He said workers deserve a "fair share of the benefits" that they help to create for their employers.

Biden has called himself "the most pro-union president" in US history. The UAW endorsed him during his 2020 election campaign. He said he is sending his labor secretary to help negotiate what he calls a "win-win contract."