Fiat, the Italian car manufacturer, is expected to present its plans to buy German Opel, part of General Motors' European operations.

The Italian company has also sealed a deal to take a stake in Chrysler, the bankrupt US car maker, in an effort to become the world's second biggest car manufacturer.

A spokesman for Fiat said the company would be offering assets instead of cash to purchase part of Opel.

The German government has set Wednesday as the deadline for bids to buy the the GM operations.

Sergio Marchionne, chief executive officer of Fiat, has said any merger with Opel will not cause Italian manufacturing plants to close.

His comments come after thousands of workers marched in Turin, Fiat's hometown, on the weekend over concerns about the company's move to take over GM Europe's operations.

"Marchionne has always said and maintained, also in recent days, that closures in Italy are not foreseen," Claudio Scajola, Italy's industry minister, told the Corriere della Sera newspaper on Wednesday.

"The strategy would be to aggregate around Turin (both) Chrysler and Opel to create the second-largest group in the world, with the greatest volumes and most evolved products. I would be more concerned if Fiat would have remained still, or if it had been Opel to buy it."

Marchionne has been meeting officials in Germany to lay out his plans to take on Opel.

He also has reached a deal for Fiat to take a controlling stake in Chrysler, an operation that will be completed once the US firm emerges from bankruptcy.

Fiat has said it plans to create a new company that would group brands including the Fiat, Lancia and Alfa Romeo with GM's European operations including Opel, and to list it on the stock market.