Former defence secretary Gotabaya Rajapaksa, who is also the brother of Mahinda Rajapaksa, is likely to be announced as the candidate of the Sri Lanka Podujana Peramuna (SLPP), the main party of opposition alliance.
Mahinda Rajapaksa, who is leader of opposition now, will also take over as the leader of SLPP at its first national convention in Colombo this afternoon.
SLPP is a breakaway faction of Sri Lanka Freedom party (SLFP) led by current President Maithripala Sirisena. Both SLFP and SLPP are having talks for an alliance before the polls and will have a common candidate.
United National Party (UNP) led by Prime Minister Ranil Wickremsinghe is the other main party which is divided over the issue of Presidential candidate. Mr. Wickremsinghe plans to contest the elections but is facing stiff contest from UNP deputy leader Sajith Premadasa.