Bulgaria will call a tender for six new engines for its MiG-29 fighter jets and the relevant spare parts by the end of the month, Defence Minister Nikolay Nenchev said on Tuesday.

Nenchev was taken on a test flight of a MiG-29 with engines provided by Poland under an agreement signed with Bulgaria last year. Under the deal Poland will repair six engines for the twin-engine Soviet-made fighter aircraft of the Bulgarian Air Force.

Meanwhile, Poland has lent two engines to be used on Bulgarian MiG-29s until the repair of the six engines is completed. The agreement has drawn criticism from Russia who said Poland works wasn’t licensed for the repair by the Russian manufacturer.

"I have no doubt that the Bulgarian Air Force will be able to fulfil its obligations," Nenchev said at Graf Ignatievo Air Base near Plovdiv, in southern Bulgaria, where the test flight took place, according to a statement of the Defence Ministry.

Bulgaria’s Prime Minister Boyko Borisov, who was also present at Graf Ignatievo, said that the money for the supply of six new engines for the country’s MiG-29s has already been included in the government budget.

Borisov also said that the repair of Bezmer Air Base, in southeastern Bulgaria, was expected to be completed by the end of March 2016.

Poland’s ambassador to Bulgaria Krzysztof Krajewski, who also attended the event, that the test flight of the Bulgarian MiG-29 on Tuesday was a result of successful cooperation between Bulgaria and Poland within NATO, which will continue, according to the statement.