"We do not take this lightly", Terry Dittes, the UAW vice president in charge of the union's relationship with GM, said at a news conference in downtown Detroit on Sunday.
A statement issued by GM revealed that it had offered the workers union more than $7 billion in new investments, 5400 more jobs, and various pay and benefits increases.
Roughly 49,000 workers at General Motors plants in the US planned to strike just before midnight Sunday, but talks between the UAW and the automaker will resume.
Any deal the UAW reaches with GM would set a precedent for the jobs, wages, benefits that the union demands from Ford Motor Co and Fiat Chrysler Automobiles NV.
US labor contract talks reached an impasse on Sunday, the and the UAW called for the first nationwide strike at GM in 12 years. GM countered and said its offer was fair.
GM argues the plant shutdowns are necessary responses to market shifts, and that UAW wages and benefits are expensive compared with competing non-union auto plants in southern US states. Such a slowdown could make it harder for the UAW to win concessions in the years ahead.
A source close to the UAW with direct knowledge of negotiations said most of the proposals the company disclosed publicly on Sunday came very late in negotiations Saturday.
A strike by 49,200 union workers would bring to a halt GM's USA production, and would likely stop the company from making vehicles in Canada and Mexico as well.
"GM strike is official as UAW autoworkers cur shift early and take position at 11:59a.at Flint Assembly", she wrote (formatting adjusted).
UAW members who show up at the picket line will get $250 a week.
To save money for those efforts, GM has already halted operations at three US plants - two transmission factories and an assembly line in Lordstown, Ohio. There are also four electric trucks coming that other UAW plants will build.
GM argues that its wages and benefits are among the best in the industry. In that same time period, sales of sedans have dropped 10 percent to 22.9 percent of market share, according to Experian, while sales of crossovers have grown 10 percent to make up almost half of all new cars sold in 2018.
Many union-ambivalent workers cited the corruption scandal in UAW's recent high profile defeat in its attempt to unionize Volkswagen's Chattanooga plant in June. GM has always been criticized by President Donald Trump for moving production to Mexico as well as closing assembly plants in OH and MI, which could be key states in the elections in 2020. "Get together and make a deal!" But supplies of the Chevrolet Tahoe and Suburban large SUVs, which generate big money for the company, are well below the industry average. GM now has too much USA factory capacity, especially to build slower-selling cars. The union wants to limit GM's use of temporary workers in its plants, and narrow the pay gap between new hires and veteran workers. Union members working Sunday were to report as scheduled.