Bulgaria's most successful football club CSKA Sofia looked almost certain Monday to lose its professional licence because of debts together with crosstown rivals Lokomotiv Sofia, officials said.

Pending a final decision by the Bulgarian football union (BFU) in mid-June -- seen as a formality -- the two sides now face relegation and a start next season in the amateur fourth division.

It also means that Lokomotiv Sofia will lose the right to compete in next season's Europa League after finishing third this season, two places above CSKA. Lokomotiv will be replaced by Litex Lovech.

According to press reports, CSKA owes 11 million leva (5.6 million euros, $6.1 million) and Lokomotiv Sofia about a million leva to the tax office, the National Revenue Agency.

CSKA, one of Bulgaria's most popular clubs, have won the Bulgarian league a record 31 times but have been beset with severe financial difficulties after being sold by businessman Vasil Bozhkov in 2006.

Since then the club has gone through frequent changes in ownership and numerous coaches, and were already threatened with losing their licence in 2013.

The announcement Monday came after the "appeals unit of the licensing commission confirmed the previous decision to refuse to issue licences to CSKA Sofia and Lokomotiv Sofia," the BFU said.