Massimo Sarmi told the business daily Il Sole 24 Ore on Saturday that he aimed to complete preparations to list the stake in Poste Italiane by July but that the shares might not come onto the market until a few months later unless there were a particularly good market opportunity.

Economy Minister Fabrizio Saccomanni said following cabinet approval of the sale on Friday that he hoped the operation could be completed before the summer, but Sarmi said it may take slightly longer.

"My personal target is to be ready on a technical level by July. We'd then reasonably complete the listing in September-October," he said. "But if everything is ready and there's a very favourable window in July, I want to have everything ready to take advantage," he said.

The sale of the stake to institutional and retail investors as well as post office employees is expected to raise 4 to 4.8 billion euros $5.5 billion (3.3 billion pounds) - $6.6 billion (4.0 billion pounds) and could be followed by further tranches, Saccomanni said.

It forms part of a broader package of privatisations aimed at chipping away at Italy's huge public debt, including the sale of a 49 percent stake in air traffic control company ENAV, which was also approved on Friday.

(Reporting By James Mackenzie; Editing by Hugh Lawson)