The United Auto Workers and General Motors have reached a tentative agreement that could end a monthlong strike by nearly 50,000 workers, according to the union and the company.

Union leaders said the proposed agreement "represents major gains" for workers, although they would not comment on the details. A council of UAW leaders is scheduled to vote on the proposed agreement Thursday, which would then go to a vote by the union's full membership.

The tentative deal does not immediately end the strike. As they vote on the proposed agreement Thursday, UAW leaders will also consider whether to end the strike or continue it until the full membership vote.

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Workers left their jobs early September 16. They wanted a bigger share of GM's profits as well as greater job security and a path to permanent jobs for thousands of temporary workers in GM factories. The company wanted to reduce labor costs to a level closer to U.S. factories run by foreign automakers.

The deal is likely to include some pay raises, lump sum payments to workers, and requirements that GM build new vehicles in U.S. factories, the Associated Press reports. Early on, GM offered new kinds of autos and parts to be made in Detroit and Lordstown, Ohio, two of the four U.S. cities where it planned to close factories.

The company offered to build a new electric pickup truck to keep the Detroit-Hamtramck plant open and to build an electric vehicle battery factory in or near Lordstown. The battery factory would employ far fewer workers and pay less money than the GM assembly plant slated to close there.

The strike comes at an uncertain time for the U.S. auto industry, with auto sales having reached an apparent peak and U.S. tariffs on steel and aluminum raising companies' costs.

The unions argue that they had given up pay raises and made other concessions to keep GM afloat during its 2009 trip through federal bankruptcy protection. Now that GM has been nursed back to health, earning $2.42 billion in its latest quarter, workers want a bigger share.

The strike has shut down 33 GM manufacturing plants in nine states across the U.S. and cost the company more than $1 billion in lost profits, according to some analyst estimates It was the first national strike by the union since a two-day walkout in 2007 that had little impact on the company.

CBS News' Costanza Maio contributed reporting.