DETROIT — General Motors and the United Auto Workers union have reached a tentative deal for a new four-year labor deal, moving the sides closer to ending a month-long strike.

The deal is subject to approval by the union’s national GM council during its meeting on Thursday and then must still be ratified by the wider membership, the UAW said in a statement. The strike continues at least until Thursday’s meeting.

If the council approves the deal, it would decide whether to end the strike at that point or continue until the wider membership votes.

“The No. 1 priority of the national negotiation team has been to secure a strong and fair contract that our members deserve,” UAW Vice President Terry Dittes, director of the union’s GM department, said in a statement. He said the union would not release details of the agreement until after the Thursday meeting.

GM officials confirmed a tentative deal had been reached, but declined further comment.

The strike began on Sept. 16, with about 48,000 hourly workers of the UAW union at GM seeking higher pay, greater job security, a bigger share of profit and protection of healthcare benefits. Other issues included the fate of plants GM has indicated it may close, and the use of temporary workers.

The Center for Automotive Research (CAR) in Michigan has estimated the strike’s weekly costs to GM and the UAW strike fund at $450 million and $12 million, respectively. Analysts had said investors were comfortable with a strike that was costly upfront as long as the No. 1 U.S. automaker maintained its long-term financial and strategic flexibility.

Details of GM’s last offer emerged over the weekend and included an increase of its proposed ratification bonus by $1,000 to $9,000. GM also proposed 3% pay raises in the second and fourth year of the four-year-contract and 3% and 4% lump sum payments in the first and fourth year respectively. It agreed to make temporary workers with three years of service permanent and give those workers a $3,000 ratification bonus.

If the deal is approved by the workers, the union will next begin negotiations with Ford Motor or Fiat Chrysler Automobiles (FCA), covering many of the same issues regarding healthcare costs, job security and the use of temporary workers. The UAW previously agreed to temporary contract extensions with both automakers while it focused on GM.

A successful ratification is not a sure thing as workers during the 2015 talks initially rejected a deal with FCA before eventually approving a deal that had been tweaked after further negotiations.

This year’s talks have been overshadowed by a widening federal investigation into corruption at the union.

However, UAW officials and striking workers on the picket lines said their focus in the dispute with GM was on jobs, pay equity and fairness for workers who made concessions in 2009 to help GM through its government-led bankruptcy.