SOFIA (Reuters) - The United States, Sweden and Italy have filed bids to supply Bulgaria with eight fighter jets aimed at replacing its ageing Soviet-designed MiG-29s, in a tender estimated at 1.8 billion levs ($1 billion), the defense ministry said on Monday.

The United States offered two options: either new Lockheed Martin F-16V jets or new Boeing F-18 Super Hornets. Sweden offered new Saab Gripen jets, while Italy proposed supplying second-hand Eurofighters.

“The offers will be assessed and then a political decision will be taken,” Deputy Defence Minister Atanas Zaprianov told reporters upon the offering of the bids.

He declined to comment how long the process would take, including direct negotiations with the preferred bidder.

The deal will help Bulgaria, which joined NATO in 2004, improve its compliance with the alliance’s standards.

It is Bulgaria’s biggest military deal, and the tender had to be relaunched this year after a parliamentary commission ruled last year that a previous tender needed to be relaunched. In the previous tender, the Gripen jets had been favored.

NATO has encouraged its eastern members to develop, buy and operate new equipment made by alliance countries.