The parliamentary security commission found that the "choice of jet made by the Federal Council carries the most risks: technically, commercially, financially and in respect of the delivery date", Swiss news agency ATS reported.
The members of the commission, all appointed by the Swiss parliament's National Council of representatives, nonetheless voted 16 to 9 against demanding that ministers put a halt to the deal.
Defence minister Ueli Maurer who is in charge of the dossier said that negotiations with Sweden were "reaching their conclusion (and) will allow us to resolve any outstanding issues".
The purchase price, some 3.126 billion francs ($3.25 billion), has been guaranteed not to change, he said, adding that the Gripen "was the cheapest" option compared with both Dassault Rafale and the Eurofighter.
Opponents of the JAS Gripen purchase announced that they would seek to hold a national referendum on the deal.