The United Auto Workers will continue its strike against General Motors Co. until a tentative deal is ratified by its full membership, extending their walkout for at least another week.

Voting on the proposed contract will begin Oct. 19 and ballots will be due by Oct. 25, Brian Rothenberg, the UAW's spokesman, said during a press conference Thursday in Detroit. The strike began Sept. 16 and has cost GM an estimated $2 billion.

GM shares fell 0.5 percent to $36.02 in late trading. The stock is down about 7 percent since the strike began.