* German, French, Swiss firms among bidders
* Colombian president backs his country's bidder
* Colombians also seek to buy TAP airline (Adds Colombian president, Avianca interest to buy TAP)
LISBON, Nov 15 (Reuters) - Portugal stepped closer to selling airport operator ANA, picking five out of eight preliminary bidders to make binding bids in a sale that could reap over 2.5 billion euros ($3.20 billion) for the indebted state.
Lisbon is betting on infrastructure deals to cut its debt, which it must do as a condition of its 78 billion euro international bailout, as demand for regulated assets in Europe remains strong despite the region's debt crisis.
It has so far sold stakes in power companies EDP and REN, mainly to Chinese investors.
The government said on Thursday potential bidders for ANA included German airport operator Fraport, French construction firm Vinci and Zurich airport operator Flughafen Zurich.
The other two are the Blink consortium that includes Portuguese builder Mota-Engil and Colombian construction company Odinsa, and the Eama consortium grouping Argentinian infrastructure group Corporacion America and Portuguese group Sonae, among others.
Brazilian firms that sources said were among potential bidders were apparently left out.
Treasury Secretary Maria Luis Albuquerque said some of the offers were 12 to 13 times ANA's earnings before interest, taxes, depreciation and amortization (EBITDA), which puts them between 2.4 billion euros and 2.6 billion euros based on ANA's 2011 EBITDA of 200 million euros.
"The selected offers coincide with the best prices at this nonbinding phase, but they also take into account the strategic point of view," she said. "Binding offers have to be presented by mid-December."
Visiting Colombian President Juan Manuel Santos spoke on Thursday of a "clear potential to broaden ties between the two countries" via the air travel sector.
"The synergy that it generates is evident and it would be a very positive step as it has geographical logic," Santos told reporters.
Colombian-Brazilian tycoon German Efromovich, who controls Colombia's Avianca airline, is also vying to buy Portugal's TAP carrier.
Portuguese Prime Minister Pedro Passos Coelho said he saw "the Colombian interest with very good eyes."
Portugal's government hopes to use 1 billion euros of proceeds from the airport concession sale to cut this year's budget deficit and meet the 2012 target set by its lenders.
Europe's independent statistics agency Eurostat is still analysing the issue. Privatisation revenues can be used for government debt reduction, but not for deficit cuts. ANA is to be sold off initially under concession terms, which the government insists qualifies the money for use in deficit cuts. ($1 = 0.7817 euros) (Reporting By Sergio Goncalves, Daniel Alvarenga; Writing by Andrei Khalip; Editing by Helen Massy-Beresford)