FILE PHOTO: A Finnish Air Force F/A-18 Hornet fighter participates in the Arctic Challenge Exercise 2015 (ACE15) in Rovaniemi, Finland May 27, 2015. Lehtikuva/Kaisa Siren via REUTERS

HELSINKI (Reuters) - Finland invited bids on Friday to supply 64 multi-role fighter aircraft to replace its ageing fleet of F/A-18 Hornet jets, due to be phased out from 2025.

The deal is expected to cost 7-10 billion euros ($9-12 billion). Possible candidates include Saab’s Gripen, Dassault’s Rafale, Boeing’s Super Hornet, Lockheed Martin’s F-35 and the Eurofighter, a joint project by Airbus, BAE and Leonardo.

“If we want to keep defending the entire Finnish territory in a credible way, this is a necessity, especially as we do not belong to a military alliance,” defense minister Jussi Niinisto told a news conference.

He said performance of the jets would be the main criterion and Finland was committed to thorough talks with all plane makers.

U.S. President Donald Trump suggested last year that Finland had already chosen Hornets, made by U.S. group Boeing, but Finland denied that.

Helsinki is asking manufacturers to provide price quotations for the new jets by early 2019, and plans to make the final decision in 2021.

Finland shares a 1,340km (833 miles) border and a difficult history with Russia. It has compulsory military service for all men and is one of six members of the European Union that have not also joined NATO.