DETROIT, US (AFP) - Ford Motor Co. reached a tentative deal with its main union that includes the same concessions granted to rivals General Motors and Chrysler as they restructured under bankruptcy protection, union sources said Tuesday.

The United Auto Workers said the deal was "overwhelmingly" approved by union delegates Tuesday, but declined to confirm the details until its members have an opportunity to vote.

However, union sources said it includes key changes such as a no-strike clause for the 2011 contract which would extend through 2015, work rule changes and a six-year wage freeze for any new hires.

The agreement - which would cover about 41,000 Ford workers - follows the historical pattern of replicating contracts at the Detroit Three automakers to avoid unfair advantages.

Ford also received major concessions in February such as the elimination of automatic cost of living adjustments, dramatically reduced health care costs and deferral of previously agreed future raises.

"This agreement is another step in meeting the challenges of a very difficult time in the US auto industry, and we look forward to presenting it to UAW Ford workers," UAW President Ron Gettelfinger said in a statement.

Union sources said Ford was offering more work at various plants and US$1,000 (S$1,399) bonuses in exchange for the contract changes, which have run into opposition from some local union officials and workers.

"Accepting a no-strike clause would be like letting the company bust the union," said Gary Walkowicz, a bargaining committeeman at the Dearborn Truck Plant who has been critical of the union's concessions in the past.

"We would have no bargaining power in 2011 when Ford might be making big profits again," Walkowicz said in a note which was circulated on the Internet.

"Not only would this mean that we would not get back the concessions we have already lost, it would also mean an arbitrator could lower our wages even further."

Ford declined to comment on the content of the deal, but said it would help the company "improve its current and long-term competitiveness in the United States."