A second round in the presidential ballot will take place on July 7, it said in a statement that was also signed by the other two parties in the current coalition, the leftist Ettakatol and the secular centre-left Congress for the Republic (CPR).

The three parties have also agreed on the political system to be enshrined in the constitution of the North African country that sparked the Arab Spring protests when it ousted longtime dictator Zine El Abidine Ben Ali in January 2011.

The parties have agreed "on a mixed political system in which the president will be elected by universal suffrage for a better balance of power, including at the heart of executive branch."

Disagreements over the nature of the political system has been delaying the drafting of the new constitution by Tunisia's interim parliament.

The Islamist Ennahda has been pushing for a purely parliamentary system, while the other parties have wanted important powers to remain in the hands of the president.

A first draft of the constitution is due to be submitted to the Assembly in November, and then each article is to be debated between December and January before parliament votes on the text.