TUNIS (Reuters) - The Tunisian president's secular party threatened on Sunday to withdraw from the Islamist-led government unless it drops two Islamist ministers.

The moderate Islamist Ennahda party won 42 percent of seats in the country's first post-Arab Spring elections in October 2011 but formed a government in coalition with two secular parties, President Moncef Marzouki's Congress for the Republic and Ettakatol.

Coalition discussions on a cabinet reshuffle have broken down after Congress for the Republic asked for the replacement of Foreign Affairs Minister Rafik Abdessalem, who is son-in-law of Ennahda head Rached Gannouchi, and Justice Minister Nouridine Bhiri, saying their performances had been weak.

"If Ennahda does not change its foreign and justice ministers within a week, the Congress for the Republic will withdraw its ministers from the government and President Marzouki may resign from his post," said Mohammed Abbou, secretary-general of Congress for Republic.

Tunisia, the first Arab country to oust its leader and hold free elections as uprisings spread around the region two years ago, has so far made a relatively smooth transition to democracy, but analysts say a secular-Islamist rift in the coalition could disrupt that process.

(Reporting by Tarek Amara; editing by Andrew Roche)