(Reuters) Bulgaria’s defense ministry has signed a 21.8-million euro ($23.75 million) contract with Sofia-based company Aviostart for the supply of 10 Russian engines for its aging fleet of Russian MiG-29 jet fighters, it said on Thursday.

The deal includes the supply of four new and six repaired engines. The first two engines will be delivered by the end of next April, the ministry said, adding that the deal will ensure the operations of the Black Sea country’s air forces.

“Bulgaria has nine operational aircraft at the moment and the deal, which was signed on Wednesday, would allow this number to rise to 14,” the defense ministry spokesman said.

Last year Bulgaria signed an agreement with NATO ally Poland to repair six MiG-29 fighter jets, part of a push by the Balkan country to reduce its reliance on Russia.

The ministry signed the deal with Aviostart after failing to attract any other offers which were qualified to supply it with the Russian-made engines, which must be certified by Russian Aircraft Corporation MiG.

Prime Minister Boiko Borisov said Bulgaria is holding talks with Russia to overhaul the aging MiG-29 fleet at Bulgaria’s state-owned military plant Avionams.

The Balkan country is also planning to buy eight new or second-hand fighter jets next year to help to revamp its air force and improve its compliance with NATO standards.