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By Cyril Altmeyer and Jessica Mead

PARIS, July 7 (Reuters) - France's post office is mulling a partial privatisation aimed at raising 2 to 3 billion euros to prepare one of the bastions of full state ownership for European competition, a source close to the matter said on Monday.

Confirming media reports, the source said the move would value La Poste and its mail-to-banking business at 10 billion euros ($15.65 billion), half the value of its equivalent in Germany which France views as a threat as Europe gears up for liberalisation in 2011.

"These figures are not incoherent," the source said, asking not to be named because the discussions are continuing.

French President Nicolas Sarkozy's chief of staff lifted a taboo on ownership of the postal service, which is one of the country's biggest employers with 280,000 staff, on Sunday by saying the idea of a stock market listing "deserves interest".

The move would be part of France's efforts to prepare itself for the liberalisation of the European postal market by 2011.

But it was immediately attacked by unions, already involved in sporadic strikes to defend pensions and the 35-hour week.

The Sud-PTT postal union said it would be "the end of the public postal service" and that a similar step taken by France Telecom (FTE.PA: Quote, Profile, Research) had merely saddled it with massive debts.