MADRID (Reuters) - Talgo's top shareholder is in talks to sell its 40% stake in the Spanish train maker to Swiss rival Stadler Rail as an alternative to a tender offer from Hungary's Ganz-Mavag consortium, El Economista newspaper reported on Monday, citing unidentified market sources.

On March 7, Ganz-Mavag - which includes the Magyar Vagon rail group - offered 619 million euros ($669 million) for all of Talgo's shares. The bid was opposed by Spanish Transport Minister Oscar Puente, who was quoted by local media as saying the government would do "everything possible" to prevent the takeover.

According to El Economista's report, Trilantic sees Stadler as an alternative buyer of its 40% stake that could "complement its product range with Spanish high-speed and variable gauge technology".

However, Stadler would have to launch a full takeover bid for the whole company, as Spanish legislation requires a mandatory tender offer when a buyer wants to acquire more than 30% of any publicly traded company.

Stadler and Trilantic did not immediately respond to requests for comment.

Since Ganz-Mavag filed its offer to stock market regulator CNMV, the Spanish government has repeatedly said that Talgo is a strategic company and that the deal requires its approval given Talgo's access to sensitive information on the country's railway network and, by extension, national security.

The Swiss train builder already has a subsidiary in Spain, Stadler Rail Valencia, as well as a factory in the country's east and ongoing orders contracted by state-owned rail operator Renfe, the El Economista report added.

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