WASHINGTON — Some lawmakers are seeing positive signs as the ink dries on a new auto partnership even as the future of the Fenton assembly plant remains murky after the Obama administration rejected both the Chrysler and GM restructuring plans today.

Chrysler formed a deal with Italian auto maker Fiat less than an hour after President Obama spoke this morning, saying the American company couldn’t survive on its own. A federal assessment of Chrysler called for the company to merge with Fiat within 30 days before the White House considered another $6 billion loan.

Rep. Russ Carnahan, D-St. Louis, said the partnership with Fiat would help Chrysler by supplying more fuel efficient engines and could help the Fenton plant as well.

The federal assessment released today listed one of Chrysler’s weaknesses as a lack of flexible manufacturing. This may be one strength the Fenton plant has. It was retrofitted in 2007, allowing it to produce trucks, minivans and cars with European specifications.

“There may be some additional cutbacks in the work force and plant closings in this process and we don’t know where those will be,” Carnahan said in an interview. “But I think the Chrysler plant in Fenton — this is a critical time for them to market the value that they will bring to building a new generation of vehicles today.”

Half the Chrysler Fenton plant, located outside St. Louis, has been idled since October, the rest of the facility has been running on diminished production.

Chrysler said in its restructuring plan last month that it will close two assembly plants and five engine plants by 2014. Experts said last month that Fenton was in danger of closing.