Germany denied it was considering a possible breakup of carmaker Opel ahead of a crucial final round of meetings on Tuesday between the government and top executives from Italian suitor Fiat .

Fiat Chief Executive Sergio Marchionne was due to meet Chancellor Angela Merkel on Tuesday morning to try to address Berlin's concerns about his bid for Opel, the Ruesselsheim-based unit of U.S. carmaker General Motors .

Fiat Vice Chairman John Elkann was also in the German capital and due to meet Economy Minister Karl Theodor zu Guttenberg.

Guttenberg's ministry denied a report in German daily Bild that he had evoked the possibility of an Opel liquidation in an internal paper after deciding that none of the three offers for the carmaker was economically sustainable.

In addition to Fiat, Canadian car parts group Magna and Belgium-listed industrial holding RHJ International have also submitted offers for Opel.

There is no such economy ministry document, a ministry spokesman said. The document in question was provided by an external consulting firm and did not reflect Guttenberg's view, the spokesman added.

The German government has made clear that GM will have the final word on who buys Opel, but Berlin will play a crucial role in that decision because it is being asked to cough up billions of euros worth of loan guarantees as part of any deal.

Opel has 25,000 workers at four plants in Germany and the carmaker's fate has become a politically charged topic of debate in Berlin ahead of a federal election on September 27.

Merkel said on Monday that pressure to choose a preferred bidder was building ahead of a June 1 restructuring deadline for GM set by the U.S. government, which could lead to a Chapter 11 bankruptcy filing by the Detroit-based carmaker.

Merkel is due to host a top-level meeting on Wednesday evening where the German government is expected to settle on a preferred bidder.

Last week top ministers said the Magna bid, which is backed by Russian investors, looked to be the best of the three.

But since then, all three of the bidders have improved their offers, the government said, leaving a down-to-the-wire race for control of Opel, a group that traces its roots in Germany back to the 19th century.

Magna and RHJ are expected to present their plans to Opel's European labor representatives at the carmaker's headquarters in Ruesselsheim later on Tuesday.

Magna has said that under its plan, Opel's employees would receive a 10 percent equity stake in the company, and sources familiar with the matter have told Reuters that RHJ has a similar proposal.

(Writing by Noah Barkin; Editing by Jon Loades-Carter)

Germany