DETROIT – Democratic presidential candidate U.S. Sen. Elizabeth Warren, of Massachusetts, protested with General Motors workers Sunday, expressing solidarity with them.

Warren participated in a "Solidarity Sunday" protest at the GM Detroit-Hamtramck Assembly plant. Large crowds packed the Detroit-based plant Sunday and marched alongside Warren.

Similar Solidarity Sunday protests are being held around the country in support of GM workers and members of the United Auto Workers.

Protestors chanted, "UAW, stand strong," "No contract. No peace," and "We are the union. The mighty, mighty union."

Warren encouraged protestors to "be strong." She criticized GM for making billions of dollars in profits last year, and closing down plants.

"Their own loyalty is to their own bottom line. The workers of the UAW are here to say, 'no more.' They want a fair wage. They want benefits. Everybody deserves a living wage in this country," Warren said.

She thanked UAW members for standing up for the rights of workers. "I know this is hard to do without your paycheck. This is the time when we find out who people are. You do well, American workers do well across the country. Lets be clear, unions built America's middle class," Warren said.

Michigan Democratic Rep. Andy Levin also spoke at the protest. "This is a fight for the soul of America," Levin said, adding that GM needs fewer temporary workers and more full-time jobs.

Sunday marks the seventh day of the nationwide UAW strike against GM.

Leaders of the union decided to initiate a national strike Sunday, Sept. 15, against the automaker. By Monday morning, nearly 50,000 union members had stopped reporting to work.

Things seem to be moving forward on negotiations between General Motors and the UAW. Sources tell Local 4 "good progress" was made Saturday between the union and GM.

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Overall, union workers have shut down 33 manufacturing plants in nine states and 22 parts distribution warehouses. Negotiations between the two parties have been underway all week, but it's unclear when a new deal could be reached and when the strike will end.

Meanwhile, about 1,200 Canadian auto workers have been laid off due to parts shortages.

The UAW said workers are striking to secure fair wages, affordable healthcare, their share of profits, job security and a defined path to permanent seniority for temp workers.

GM said it presented "a strong offer that improves wages, benefits and grows U.S. jobs in substantive ways."