ROME (AP) -- Fiat won't improve its offer for Opel but remains interested in taking over the European unit of General Motors Corp., the Italian carmaker's CEO said Friday.

Sergio Marchionne told reporters that a tentative Opel deal by rival bidders Magna International Inc. and Russia's Sberbank "is not doing too well."

"We have confirmed our interest," Marchionne said on the sidelines of a Venice conference on Italy-U.S. relations. "I don't think Fiat's offer can be improved. It's the most rational thing from an industrial point of view that we could offer."

Sberbank also warned on Friday that the Magna bid could still fall through ahead of a July deadline to sign a preliminary agreement.

Marchionne also spoke of Fiat's takeover of Chrysler, which allowed the U.S. automaker to emerge from bankruptcy protection.

Marchionne, who is the new Chrysler's CEO, said that returning the loans given to the company by the U.S. Treasury is "the key point of our agenda."

He said he believes Chrysler could present its new product range in the next two weeks.

Earlier this month, Fiat closed a deal to take a controlling stake in the failed U.S. automaker in exchange for technology and management know-how that will help the new Chrysler focus on smaller and more efficient vehicles.

Fiat also plans to launch in North America its successful remake of the iconic Cinquecento, or 500, compact and the sporty Alfa Romeo brand.

Marchionne said Friday that Fiat would decide in the coming days which Chrysler plant will produce the 500 models destined for the U.S. market.