Rejecting for a moment the notion that imitation is the highest form of flattery, a high-level Ford Motor Co. engineer says General Motors Corp. engineers infringed on at least one Ford patent when they designed the new third door on Chevrolet and GMC extended-cab pickups.

A Chevy spokesman claims it's not true, and says Ford is just mad that Chevy has beat them to the punch in the marketplace. Chevy's 3-door trucks went into production in late November. Ford's went into production a few weeks later. The extra door is standard on the Fords, an option on the Chevys.

Thomas D. Baughman, Ford's chief program engineer on the F-Series, tells a small group of reporters that he is convinced GM has infringed on Ford patents and he expects Ford lawyers would soon be contacting GM. However, he stopped short of saying that Ford would actually file a formal suit. Insiders say these type of disputes -- especially among the Big Three -- typically are settled quietly behind closed doors.

Chevrolet spokesman William J. O'Neill says GM and Ford attorneys have discussed media reports of the dispute, but no legal discussions or negotiations have taken place.

The third doors in both automakers' vehicles are similar expect for seat belt and handle placement. Mr. Baughman argues that Ford developed the concept of a 3-door extended cab and applied for a patent that was issued in 1989. GM says it has used a similar door on its full-size G-vans since the 1960s. Mr. O'Neill says GM developed the third door for its extended cab pickup in a special 23-month crash program.

Interestingly, both automakers apparently worked with the same supplier to develop the third-door concept. The supplier could not be identified by press time.