ZURICH, June 21 (Reuters) - Lockheed Martin"s (LMT.N) F35-A Lightning II performed the best in a Swiss evaluation of what fighter jet to buy next, although the final political decision was still open, Swiss broadcaster SRF reported on Monday, citing three unidentified sources. The government is supposed to decide this month among the Eurofighter from Airbus (AIR.PA), the Rafale from France"s Dassault (AVMD.PA), Boeing"s (BA.N) F/A-18 Super Hornet, or the F35-A. Swiss voters in September backed the government"s plan to spend up to 6 billion Swiss francs ($6.53 billion) on new fighter jets in a surprisingly close referendum. "According to insiders, Switzerland can buy a larger number of F-35s with the budgeted 6 billion Swiss francs than would be the case with the three competitors. The F-35"s simulator could also be an asset: it would allow the F-35 to carry out significantly more virtual training missions than the competition," SRF"s investigative programme Rundschau said in a summary of a report to air on Wednesday. The defence ministry declined to comment. The aircraft will 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. At least two of the seven Cabinet members would prefer a European fighter jet, SRF said, while critics have promised to launch a referendum campaign under the Swiss system of direct democracy against any decision to buy a U.S. fighter jet. ($1 = 0.9183 Swiss francs)