Skilled trades workers have the right to reject portions of the national contract unique to them, according to the UAW's constitution, the union said.

Overall, 55.4 percent of GM's UAW workers voted to approve the contract. Production workers voted 58 percent for the deal and skilled trades workers, who are fewer in number, voted 59.5 percent to reject it.

Over the next several days, UAW leaders will meet with skilled trades workers at each work site to determine their reasons for rejecting the deal, a union statement said.

The UAW's executive board will then meet to determine next steps. But any changes to the national contract can only affect skilled trades workers, the UAW said.

"The results of this process cannot change aspects of the agreement which are common to all members," the UAW said.

Earlier on Friday, the union and Ford Motor Co announced that a tentative agreement had been reached for Ford's 52,700 UAW members at Ford. The Ford pact will go to a worker ratification vote as early as next week.

GM also has 52,700 UAW members.

The 40,000 UAW workers at Fiat Chrysler Automobiles last month ratified their new four-year contract, which has already gone into effect.

(Reporting by Bernie Woodall; Editing by Lisa Shumaker and Ken Wills)

By Bernie Woodall