The governing United National Party (UNP) called for the election after the opposition blocked several key reforms, thwarting Sirisena's pledge to return Sri Lanka to a parliamentary-style democracy.
"There is now a necessity for an immediate dissolution of parliament," UNP treasurer Eran Wickramaratne said in a statement.
"The (current) political uncertainly will have dire economic consequences."
"The only way out is for the people to be given the chance to decide (at elections)."
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Parliament yesterday passed reforms to curb the powers of the president, including restoring a two-term limit -- reversing changes made by strongman Mahinda Rajapakse during his decade-long rule.
But the ruling UNP was forced to compromise on other reforms to secure the support of the opposition, whose votes were crucial to gain a mandatory two-thirds majority in parliament.
Sirisena's government does not enjoy a majority in parliament.
The bill removed the president's power to dissolve parliament until it has completed four and a half years of its five-year term.
The amendment was watered down, however, to ensure that the minority government secured the opposition's support.
The government also agreed to accommodate four more legislators in a new body which will make key appointments to run 11 public institutions such as the police, the judiciary, the elections office and the civil service.