SOFIA (Reuters) - Bulgaria has sent a request for proposals (RFP) for 16 new or used fighter jets to replace its aging Soviet-designed MiG-29s to seven countries, the defense ministry told Reuters on Wednesday.

The Black Sea country, which joined NATO in 2004, has called for bids to supply aircraft from the United States, Portugal, Israel, Italy, Germany, France and Sweden.

Last month Bulgaria’s parliament approved a plan to buy the jets. It plans to acquire them in two equal stages as part of efforts to improve its compliance with NATO standards.

Some 1.8 billion levs ($1.08 billion) will cover the first eight aircraft, as well as ground handling, team training and three years of initial integrated logistics support.

Potential suppliers include Boeing’s F/A-18 Super Hornet, Saab’s Gripen, Dassault’s Rafale and Lockheed Martin’s F-16 or Eurofighter, the ministry said. Sofia is asking manufacturers to provide bids by October 1.

The ministry has called for bids for new or used jets from the United States (F-16 and F/A-18 Super Hornet), France (Dassault Rafale) and Sweden (Gripen C/D) as well as new jets from Germany (Eurofighter 3 Tranche) and used planes from Portugal (F-16), Israel (F-16) and Italy (Eurofighter Tranche 1).

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

Some eastern European NATO allies that were once Soviet satellites still rely on Russian-made military jets - two-thirds of Poland’s military equipment dates from the pre-1991 Soviet era, for example.

The question of which warplanes to buy has vexed successive governments in Bulgaria for more than a decade.

Sofia aims to raise its annual defense expenditure to 2 percent of the country’s gross domestic product by 2024.