Colombo: Incumbent Ranil Wickremesinghe is set to take oath as Sri Lanka's new Prime Minister of a unity government on Tuesday after his United National Party (UNP) appears close to a simple majority, with rival Mahinda Rajapaksa admitting defeat in the closely contested parliamentary polls.

Wickremasinghe, 66, would take oath in a simple ceremony at the Presidential Secretariat and the cabinet of national government would be appointed later, media reports said.