"Catastrophic consequences" await the Bulgarian armed forces if they are not weaned soon from dependence on old Russian equipment and repairs, according to outgoing Defence Minister Velizar Shalamanov.
He was speaking in a BBC interview amid a war of words that has broken out between Bulgaria and Russia over Russian involvement in Ukraine and Russian pressure to speed up work on the South Stream gas pipeline, which will cross Bulgaria.
As an EU and Nato member with strong traditional links to Russia, Bulgaria is walking a tightrope between East and West.
Bulgaria was said to have frozen work on the Russian gas pipeline project in August, under EU and US pressure. According to Russia, work on the ground continues.
Tensions between Bulgaria and Russia grew when President Rosen Plevneliev described Russia as "a nationalist and aggressive state" for its involvement in Ukraine.
Suggestions from outgoing Defence Minister Shalamanov that Bulgaria might buy used F-16s from Italy or Greece, or Eurofighters from Portugal, prompted Russian Deputy Prime Minister Dmitry Rogozin to tweet: "News from Bulgaria: a certain Shalamanov has convinced Prime Minister Bliznashki to once again betray Russia... in favour of second-hand eagles."
That comment sparked a reaction from Bulgarian Foreign Minister Daniel Mitov who said such comments were "extremely unworthy, contrary to good manners and show… a lack of respect for Bulgarian institutions".
Mr Shalamanov told the BBC that reliance on outdated Soviet-era equipment, which still needs spare parts and maintenance in Russia, was the result of 10-15 years of mismanagement of the Bulgarian armed forces.
As a result, he said, in the current Nato standoff with Russia over its role in the conflict in Ukraine, Bulgaria was having to depend on its neighbours, Greece and Romania, to help police its own Black Sea borders.
Following the 5 October elections, a new government is to be formed in Bulgaria, leaving Mr Shalamanov unusually free to speak his mind over the state of the armed forces.
"The critical area is especially air defence. Because all the radars, all the surface-to-air missile complexes and fighters were produced in the Soviet Union," he said. "And maintenance, especially of the fighters, depends very much on overhaul of the engines and other equipment in Russia."
He highlighted in particular Bulgaria's ageing fleet of MiG-29 fighters.
Bulgaria currently spends only 1.3% of its annual budget on defence, compared with a Nato target of at least 2%, re-inforced at its recent summit in Wales. The size of Bulgaria's armed forces has fallen below 30,000, down from 110,000 in 1999. The target figure was 45,000.
The outgoing defence minister spoke of Bulgaria's "high vulnerability" because of the conflict in Ukraine, although he said the situation facing its land forces was "not so dramatic" as its military industry could largely service its Soviet-era equipment such as the T-72 tank.
But he expressed concern over pro-Russian sentiment in Bulgaria.
In last week's elections "several parties… gave a higher priority to co-operation with Russia and joining a Eurasian Union, than improving our level of integration in Nato and the EU", he said.
"This creates tension and… misunderstandings, including inside the armed forces."
Asked to respond to Mr Shalamanov's comments, Volen Siderov, leader of the pro-Russian Ataka party, described the defence minister as "an American agent".
Other former Warsaw Pact armies have devised various strategies for ending their dependence on Soviet-era equipment.
In 2013 Poland launched the biggest military procurement of any Nato member, and its defence budget reached 1.95% of GDP. Hungary replaced its MiGs with Gripen fighters in 2009.
After Bulgaria, Slovakia is the most vulnerable Nato force in terms of outdated military hardware.
Around 70% of the Slovak army's land vehicles and 90% of its ammunition are past their shelf life, according to the Central European Policy Institute (CEPI) in Bratislava.