DETROIT, Oct 29 (Reuters) -

United Auto Workers President Shawn Fain is scheduled to meet Sunday afternoon with local union leaders from Ford to start the process of ratifying a new contract, while bargaining continues at General Motors following a setback Saturday.

Fain on Saturday ordered a walkout at GM's Spring Hill, Tennessee, engine plant, criticizing management's "unnecessary and irresponsible refusal to come to a fair agreement."

It is not clear what derailed GM and the UAW's progress toward an agreement patterned after earlier deals at Ford and Chrysler-owner Stellantis. Those deals won workers a record 25% jump in wages over the 4-1/2-year contract and allowed the automakers to restart their profitable truck assembly lines.

Pension costs and issues involving the use of temporary workers were among the points of contention at GM, sources said. GM said it was disappointed by the UAW decision to strike Spring Hill.

The Spring Hill walkout could hobble GM's large pickup production as well as assembly of other popular GM vehicles. Ripple effects from an extended Spring Hill strike could boost the costs of the stalemate for GM well beyond the $400 million a week the company reported last week.

GM is now the only Detroit automaker without a contract deal. Stellantis reached agreement with the UAW on Saturday and Ford on Wednesday.

GM and UAW officials are still bargaining. However, progress toward resolving the disputes could be slowed on Sunday because Fain is scheduled to attend meetings with Ford local officials in the Detroit suburb of Taylor, Michigan, and give a video update on the Ford deal at 7 p.m. ET (2300 GMT).

Union leaders will then fan out to regional meetings to explain the deals to members, who will then vote whether to approve it.

UAW leaders no longer can take ratification votes for granted. Last month, UAW workers at Mack Truck's U.S. operations overwhelmingly rejected a deal recommended by Fain. In 2015, UAW members at what is now Stellantis voted down a contract endorsed by union leadership.

The UAW will meet local union officials from Stellantis on Nov. 2 to begin a ratification process, two people familiar with the matter told Reuters.

(Reporting by Joe White; Additional reporting by David Shepardson in Washington; Editing by Lisa Shumaker)