Bulgarian prime minister Boyko Borisov has launched an initiative calling for the joint purchase of fighter aircraft, with regional allies Croatia, Romania and Turkey.
All of the nations apart from Turkey are in the process of seeking new fighters to replace their ageing fleets of legacy and upgraded Mikoyan MiG-21s or MiG-29s. The most likely candidate to replace them would be Lockheed Martin's F-16, although other systems would also be considered.
Under Borisov's so-called "smart defence" concept, the NATO members would reduce costs by placing a single order and establishing a combined air surveilance capability over their region of Europe. A pact could also include the joint training of pilots and joint exercises.
Croatia, Romania and Turkey are understood to be considering their responses to the suggestion.