CHICAGO — Truck engine maker Cummins said this week that it signed a partnership with a major unnamed car manufacturer to produce light-duty diesel engines for pickup trucks and sport utility vehicles.

The Columbus, Ind.-based company, which already makes the diesels that power some Dodge Ram pickups, said that for “competitive reasons” the customer wanted its name to remain “confidential.” Cummins only described it as “a major automotive manufacturer serving the North American market.”

Peter Nesvold, an analyst at Bear Stearns, was speculated the unnamed partner might be Nissan Motor, Japan’s second-largest car maker, Reuters reports.

It’s rumored Nisan wants to introduce a diesel version of its Titan pickup for model year 2009.

Nesvold told Reuters that Navistar International had also been bidding on the Nissan deal.

Cummins is a major supplier to Navistar for its International heavy-duty trucks.

— with files from Reuters