Burundi's president would not oppose forming a national unity government after an election boycotted by the opposition but if he wins a third term would not cut it short, a presidential official said on Wednesday.

"A government of national unity is not a problem for Pierre Nkurunziza, we are ready to do so," Willy Nyamitwe, adviser to President Pierre Nkurunziza, told Reuters after a leading opposition figure called for such a step. But he rejected the idea of cutting short any new five-year mandate as "impossible."