Sweden will have to begin replacing its ageing fighter fleet in 2020 and will need 60 to 80 new Swedish-made Gripen jets, the military said in a report handed over to the government Wednesday.

"The capability upgrade of the fighter jet system should begin in 2020 and is calculated to take 10 years," the military said in a statement, adding that "Sweden needs at least 60 to 80 planes."

"The upgrade of JAS Gripen is necessary to ensure that the fighter jet system is operatively relevant and that our air defence in the long run can stand up compared to the world around us," it added.

Swedish defence and aerospace group Saab's JAS 39 Gripen planes already make up the Scandinavian country's fighter jet fleet, but the air force wants an upgraded version with a bigger hull and more powerful engine, according to the military.

"This will allow room for more weapons and more fuel, which in turn leads to higher efficiency and durability," it said in the statement, adding that a better "radar and an improved alert- and counter-action system" were also on its wish list.

General Sverker Goeranson said it was too early to reveal the expected cost of the upgrade, although he told a news conference it would be "very expensive."

Swedish media hinted the price tag could be around 30 billion kronor ($4.5 billion, 3.4 billion euros).

The military said it's aim was to carry out the upgrades and split the cost with "at least one other strategic partner country," but did not reveal which countries it was considering.