Potential buyers of a major stake in Italian carrier Alitalia must maintain the airline's national identity, employment levels and brand, the Economy Ministry announced on Tuesday.
The ministry added that the Treasury would sell no less than 30.1% of the carrier, along with all the convertible bonds in its possession.
This meant that the state would retain at most 19.8% of Alitalia.
However, the ministry noted that according to Italian law, potential buyers must be ready to make an offer for 100% of the airline.
Other 'lock up' conditions potential bidders must meet include presenting a viable turnaround plan for the troubled airline, guaranteeing adequate national service and maintaining the airline logo.
A formal invitation for bids will be published in the press before the end of the year, after a financial advisor and legal consultant have been chosen.
The government decided December 1 to reduce the state's 49.9% stake in Alitalia by at least half in order to attract new partners for the loss-making carrier.
The decision was in line with the government's previously announced intention to help find a solution for Alitalia's future by the end of January.
Most observers believe a solution for Alitalia will hinge on finding a financial partner with funds to invest and an industrial ally, another airline with which to join forces.
Air France, which already has a 2% stake in Alitalia and is its partner in the international Sky Team alliance, is considered one of the front runners to buy into Alitalia.
There was no immediate comment from the French carrier on Tuesday's announcement.
However, ongoing 'exploratory' talks between Alitalia and Air France have apparently run aground.
Sector sources said the Italians have backed off because Air France was more interested in Alitalia as an asset than a partner and that the French wanted Italy to eliminate one of its two national hubs, either Rome or Milan, which has become a delicate domestic political issue.
Other possible suitors for Alitalia include Air China, Thai Airways and Emirates.
There has also been speculation that Italy's low cost airline AirOne was looking for a financial partner to make a domestic bid for Alitalia.
However, Alitalia cannot be too choosy because it has not reported an annual profit since 2002 and has warned that total losses for this year could exceed its 2005 losses of more than 221 million euros.
Alitalia shares have been on the rise since the government's announcement last week and gained over 5% after Tuesday's announcement.
Aside from the 49.9% held by the state, 33.229% of Alitalia is on the stock market, 9.951% is held by Walter Capital Management, 4.918% by Newton Investment Management and 2.002% by Norges Bank.
