The left-leaning "Stop-F-35" alliance handed over the 100,000 signatures required under Switzerland's direct democracy system to take any subject to a vote.

Once authorities have verified the signatures, the government will be required to set a date for a popular vote.

"This initiative is only targeting the type of plane," the alliance stressed in a statement, adding that if Switzerland choses another fighter jet, "the initiative will be withdrawn."

The Swiss government agreed in June last year to buy 36 F-35As from US manufacturer Lockheed Martin.

The purchase followed the narrow referendum approval in September 2020 for the military to spend six billion Swiss francs ($6.3 billion) to acquire a new fleet.

The F-35A combat aircraft -- already used by the US Air Force and several European countries -- was chosen ahead of the Airbus Eurofighter, the F/A-18 Super Hornet by Boeing, and French firm Dassault's Rafale.

The government said the plane was the best, but two Swiss parliamentary committees launched an investigation into why the model was chosen after a series of technical problems reported with the plane in the United States.

They also questioned the high cost of the planes.

The "Stop-F-35" alliance was formed to try to force the issue to a fresh popular vote.

But despite the concerns, the government announced in May that it wanted to speed up the purchase process, with the US offer expiring at the end of March 2023, raising fears that Bern would not wait for a popular vote on the matter.

"The government and parliament must now do everything possible to enable a popular vote and an urgent and necessary public debate about the largest military equipment contract in Swiss history," the alliance said on its website.