Who can initiate an optional referendum at the national level?

Constitution of the Democratic Republic of Timor Leste (adopted 20 May 2002)

Article 66(2). A referendum shall be called by the President of the Republic, following a proposal by one third, and deliberation approved by atwo thirds majority, of the Members of the National Parliament, or following a well-founded proposal by the Government

A one-third minority may propose a referendum, though anabsolute majority is necessary to approveit. Alternatively, the government may initiate a referendum only in cases of well-founded proposals. However, the final decision to call for a referendum rest with the president.