CAIRO — Tunisia’s ruling Islamist party, Ennahda, said on Monday that the country’s post-revolution constitution would not mention Islamic law as a source of legislation, signaling a forceful break with ultraconservatives who have been demanding an Islamic state.

Instead, a drafting committee will preserve language in Tunisia’s current constitution that refers to Islam as the state’s religion and Arabic as its language, according to Said Ferjani, a member of the political bureau of Ennahda, the Islamist party that leads Tunisia’s government.

He and other Ennahda leaders framed the decision as a bid to unify the country’s disparate political factions during a delicate political transition. “There is a huge consensus within Ennahda. We have to show leadership,” Mr. Ferjani said. “We want everyone to get involved.”

The move by Ennahda contrasted sharply with the actions of the Muslim Brotherhood in Egypt, which has angered leftists, liberals and other groups in recent days with its handling of that country’s constitution. Lawmakers associated with the brotherhood’s political wing and an ultraconservative Salafi party voted on Saturday to fill a panel that will write the constitution with Islamists, causing a walkout by members of several other parties.