The 225-seat parliament will end at midnight Friday and a new one will meet January 17 after a vote January 5, according to a presidential announcement. He said the government must go to the people for confirmation on whether the president made the correct decision when he appointed him as prime minister.
The notice will become official once it's published, and it is required to include dates for nominations for fresh elections.
The island nation was plunged into a political crisis after Sirisena sacked Prime Minister Ranil Wickremesinghe and replaced him with his former rival Mahinda Rajapaksa. Wickremesinghe has insisted his firing is unconstitutional and demanded that Parliament be summoned to prove his majority.
The party said in a Twitter message that it will meet the elections commissioner to discuss the constitutionality of Sirisena's move.
Former Sri Lankan president and the man who was sworn in as Prime Minister Mahinda Rajapaksa supported the dissolution, and said, "As leaders, it is our responsibility and obligation to give the people the opportunity to voice their opinions on the future of #SriLanka". "We will be fighting this to ensure that democracy reigns supreme in the country".
Sirisena had suspended the assembly's work until mid-November when first moving against his prime minister.
Despite Sirisena claiming Monday he had the support of 113 legislators in his bid to swap Wickremesinghe for Rajapaksa, the United People's Freedom Alliance-the political bloc led by the Sri Lanka Freedom Party-admitted that it only had "104 or 105 MPs" on its side, as AFP reported.
"The dissolution clearly indicates that Mr. Sirisena has grossly misjudged and miscalculated the support that he might or could secure to demonstrate support in the Parliament", said Bharath Gopalaswamy, director at New Delhi-based analyst group Atlantic Council's South Asia Center. Several legislators have said they were offered millions of dollars to switch allegiance and at least eight have already jumped to the president's side.
Wickremesinghe's camp is likely to contest Sirisena's move because of constitutional provisions stating a Parliament can't be dissolved until four years after its election.
The EU said on Friday, before the dissolution, that the crisis had scarred the Indian Ocean island's global reputation.
"Any further delays could damage Sri Lanka's global reputation and deter investors", it warned.