UPDATE 1-Swiss voters approve $6.5 bln purchase of fighter jets

(Adds official tally)

ZURICH, Sept 27 (Reuters) - Swiss voters backed the government's plan to spend up to 6 billion Swiss francs ($6.46 billion) on new fighter jets in a surprisingly close referendum that was won with a 50.2% majority, official results showed on Sunday.

Opinion polls had shown the plan would easily win approval in a country where armed neutrality is a tradition.

Approving funding in the binding referendum will let the government decide next year among the Eurofighter from Airbus , the Rafale from France's Dassault, Boeing's F/A-18 Super Hornet, or the Lockheed Martin F35-A Lightning II.

The aircraft would replace Switzerland's ageing fleet of 30 F/A-18 Hornets, which will go out of service in 2030.

New jets are to be delivered by 2025. ($1 = 0.9284 Swiss francs) (Reporting by Michael Shields; Editing by Alison Williams and Barbara Lewis)