The US State Department has approved the potential sale of up to eight F-16 aircraft and related equipment to Bulgaria, in a deal valued at $1.673 billion, the Defense Department said on Monday.
The principal contractor will be Lockheed Martin LMT.N, the Pentagon said.
US officials said the sale agreement was not directly related to Russia's month-long invasion of Ukraine, which prompted the Kyiv government to ask that countries that have Russian-made MiG aircraft - including Bulgaria - to turn them over for use in the fight against Russian forces.
As a former part of the Soviet bloc, Ukraine's pilots are already trained on MiG aircraft, so could use them without any delay for training.
Those MiGs would in theory be replaced with F-16s from the United States. Pentagon spokesman John Kirby said on Monday he would not characterize the sale as such "backfilling," but did not provide further details.
A source familiar with the matter said the sale had "not much" to do with the war in Ukraine, as it is part of a years-long effort by Bulgaria to modernize and upgrade its air force and improve interoperability with NATO allies.
Bulgaria announced a previous purchase of F-16s two years ago.
Another source familiar noted that the aircraft are new production, so they would not be ready for delivery for three to four years.
Bulgaria's request, the Pentagon said, included purchase of four F-16 C Block 70 aircraft; four F-16 D Block 70 aircraft; 11 engines; 11 Improved Programmable Display Generators; and 11 AN/APG-83 Active Electronically Scanned Array (AESA) Scalable Agile Beam Radars.