General Motors will halt production of its popular pickup trucks due to parts shortages, but it is not specifying which parts it needs.

The pause comes at an inconvenient time as industry experts note that GM and Stellantis have been increasing inventory in the last couple of months in preparation for a possible strike by the United Auto Workers. The UAW is in negotiations with GM, Stellantis and Ford Motor Co. as the contract the three have with the union will expire on Sept 14.

On Thursday, GM spokesman Kevin Kelly confirmed that Fort Wayne Assembly in Indiana will cancel all production the week of Aug. 28. GM makes its full-size Chevrolet Silverado and GMC Sierra light-duty pickups at Fort Wayne Assembly. Kelly said GM anticipates resuming production there on Sept. 5 after the Labor Day holiday.

Also impacted is Wentzville Assembly in Missouri, where GM makes its Chevrolet Colorado and GMC Canyon midsize pickups and the Chevrolet Express and GMC Savana vans. It will be down on third shift only for the week of Aug. 28. GM expects to restart production on third shift Sept. 5.

GM's Silao plant in Mexico has been down for the past two weeks, but will resume production on Monday. That plant also makes GM's full-size light duty pickups.

In Canada, GM's Oshawa Assembly was down Thursday due to a separate parts issue, Kelly said, but GM plans to resume production there Friday. GM builds its heavy-duty and light-duty full-sized Silverado pickups at Oshawa.

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Kelly said Flint Assembly, where GM also builds heavy-duty pickups, is running normally with no parts issues.

The production changes at Wentzville, Fort Wayne, Oshawa and Silao will not help GM's attempts to boost inventory levels whether there is or is not a strike because they all involve pickups, which are in high demand, said Sam Fiorani, vice president of Global Vehicle Forecasting for AutoForecast Solutions.

But GM's Kelly said, "We are working to limit the effect these actions will have on production volumes and inventory."

Contact Jamie L. LaReau: [email protected]. Follow her on Twitter @jlareauan. Read more on General Motors and sign up for our autos newsletter. Become a subscriber.