UNITED AUTO WORKERS VICE PRESIDENT Joe Ashton, who leads union negotiations with General Motors, says he wants the auto maker to return more production to the U.S. from Mexico.

“When we sit down at the bargaining table, we look at them bringing work back to this country,” Ashton tells journalists after an event to announce GM's $328 million investment in a Flint, MI, assembly plant for 2013 production of next-generation pickups and SUVs.

The UAW has been “crunching numbers for the last year” to make a business case for its argument, he adds.

The Flint plant, which builds heavy-duty Chevy Silverado and GMC Sierra pickups, already will take some production from Mexico later this year when the site adds a third shift to meet demand GM's Mexican operations cannot fill.

Cathy Clegg, GM vice president-labor relations, says moving production back to the U.S. is a popular topic with the UAW.

“We talk about that,” says Clegg, also on hand for the announcement. “We talk about our products, our facilities, all of the time.”

Neither side elaborates on specific products.

GM operates three assembly plants in Mexico — Silao, Ramos Arizpe and San Luis Potosi. Silao makes large pickups and SUVs; Ramos Arizpe produces the Chevrolet HHR, which is in its final year of production, as well as the Cadillac SRX, Saab 9-4X, Chevrolet Captiva and Chevrolet Chevy; while San Luis Potosi builds the Chevy Aveo B-car.

GM has shuttered assembly plants in Janesville, WI, and Spring Hill, TN, which the UAW would like to see reopen.

A third facility at Shreveport, LA, was lumped into a batch of assets slated for liquidation during GM's 2009 bankruptcy, and the UAW wants GM to take it back. It currently builds small pickups, but has no product scheduled after 2012.

Clegg says market demand will determine product allocation.

“First off, we need to see some pretty healthy market recovery before we start turning factories back on,” she says.

Until then, she says, GM will rely on capacity currently on line. The auto maker's assembly plants in the U.S. operated at 66% of capacity through the first six months of 2011, according to Ward's data.

Through June, GM's U.S. light-vehicle sales were up 17.1% against an industry that's tracking 12.7% ahead of last year.

GM's investment in Flint will save or retain about 150 jobs and is the latest in string of investments from the auto maker totaling $2 billion at 17 facilities across eight states with implications for 4,000 jobs.