(Corrects headline and first paragraph to make clear that Alstom would not give Siemens any more information than it has disclosed to GE, also corrects sourcing)
By Sophie Sassard and Jens Hack
LONDON/MUNICH May 21 (Reuters) - Alstom will not give suitor Siemens any more information about its power business than it has already disclosed to rival bidder General Electric, which has made a $17 billion approach to the French company, a person close to the French camp said on Wednesday.
Germany's Siemens has written to Alstom asking for more information ahead of a likely offer for the French firm's power business, French Economy Minister Arnaud Montebourg said on Tuesday.
The source said the request from Siemens was a "negotiating tactic".
Alstom is already in talks with GE over a 12.35 billion euro ($16.9 billion) bid for its power arm, which it is due to review by June 2. Under pressure from the French government, however, it has opened its books to Siemens as well.
Siemens has been working on an alternative proposal to swap all of its rail business for Alstom's power arm in a deal that could see France take a stake in the rail-focused French group.
But several people familiar with Siemens' thinking said on Wednesday it was likely to put its planned offer on hold until it was given more information.
Siemens declined to comment.
An Alstom spokeswoman said the company has yet to receive a formal offer from the German group and had not been given any indication of when such an offer might arrive. She did not say what extra information Siemens had requested.
The French government has criticised GE's bid, saying that a sale of Alstom's power arm would weaken the group by reducing it to its smaller transport business.
Meanwhile, the German and French governments have played up an alliance between Alstom and Siemens as a European alternative that would create two industry champions. ($1 = 0.7302 Euros) (Additional reporting by Natalie Huet in Paris; Writing by Ludwig Burger; Editing by Alexander Smith and Erica Billingham)