Shares of U.S. automakers Ford Motor (NYSE:F) and General Motors (NYSE:GM) both experienced a 1% decline in morning trade on Monday after the United Auto Workers (UAW) union issued a warning of more walkouts unless a new labor deal is reached.

UAW President Shawn Fain indicated on Friday that the automakers had reached a 23% wage hike agreement but emphasized that “more can be achieved.” While Fain hinted at a potential deal nearing, some analysts expressed concerns about the financial impact of the union’s demands on the automakers.

Wells Fargo analyst Colin Langan pointed out that the situation is becoming increasingly challenging, citing additional concessions on pensions, including higher 401K contributions and increased benefits for retirees. Despite signs of a potential agreement, Fain’s interpretation of increased offers as an indication that there’s more to gain raised concerns among experts.

The UAW’s demands include union contracts for workers at electric vehicle (EV) battery plants and the restoration of defined benefit pensions for all employees. Initially, the union had opened negotiations with a 40% wage-hike demand.

In related news, the union reached a tentative agreement with General Dynamics (NYSE:GD) over a new labor contract that covers hundreds of workers at the defense contractor’s U.S. facilities.

The ongoing strikes and negotiations with the UAW have had a negative impact on automakers’ shares. Since the contract talks began in mid-July, U.S.-listed shares of Stellantis (NYSE:STLA) have seen marginal gains. In contrast, Ford and GM shares have experienced declines of approximately 23% and nearly 27%, respectively.

Currently, Ford and GM trade at 11.34 and 4.14 times forward profit estimates, significantly lower than the S&P 500’s approximately 19.15 multiple.