Bulgarian President Rosen Plevneliev's Chief of Staff is the most likely option to take over as interim Prime Minister if a caretaker cabinet is to be formed later in December, local media report.

Rosen Kozhuharov, who heads the presidential administration, is "the only one who agreed to be Prime Minister only during Christmas," the news website Mediapool.bg quotes its own sources as saying.

Any interim cabinet appointed by the President may remain in office just until January 22, when Rumen Radev takes over as head of state and will have the right to make reshuffles or compose his own caretaker government.

"There is no way for Plevneliev to lure anyone for just a month. This is why, when it comes to appointing a cabinet, he will resort to his team of advisers," sources familiar with the issue say.

However, other sources cite the remaining uncertainty over whether Plevneliev will appoint a cabinet for a month or will stick to another plan under which Boyko Borisov will remain as Prime Minister until January 22, despite having resigned in mid-November.

An interim cabinet will have to be created if the Reformist Bloc fails to form a government within the current legislature after being handed the mandate by Plevneliev next week.