By Tarek Amara

TUNIS (Reuters) - Independents will take over the foreign and defense ministries in Tunisia's new government under a deal by the ruling Islamist party to cede key portfolios following violent unrest over the assassination of a secular opposition leader.

The new coalition of moderate Islamists, three secular parties and non-partisan figures aims to restore stability and prepare the troubled North African state, where the Arab Spring uprisings began in 2011, for elections later this year.

President Moncef Marzouki asked Interior Minister Ali Larayedh of the Islamist Ennahda party on February 22 to form a government within 15 days after Ennahda Prime Minister Hamadi Jebali resigned.

Coalition sources said Othman Jarandi, a former Tunisian ambassador to the United Nations, Oman, South Korea and Pakistan, had been named as foreign minister to capitalize on his strong ties with international bodies and the West.

Tunisia needs to negotiate a $1.78 billion loan from the International Monetary Fund. The political turmoil has set back that quest and prompted Standard and Poor's lower its long-term foreign and local currency sovereign credit rating of Tunisia.

"There is a preliminary agreement that Othman Jarandi will be foreign minister, and Abdelhak Lassoued will replace the current defense minister, Abdelkarim Zbidi, who wants to leave," a coalition source told Reuters. A second source confirmed the development but declined to give details.

Lassoued, 76, has not held a cabinet post before but served in the civil service under Tunisia's first post-independence president, Habib Bourguiba.

Ennahda said last week it would allow independent figures to take over key ministries in the next government in a concession to the non-Islamist opposition.

SOME CABINET HOLDOVERS

At least 10 members of Jebali's former cabinet will stay on, including Mohamed Ben Salem as agriculture minister and Samir Dilou as human rights minister - both members of Ennahda, as well as Culture Minister Mehdi Mabrouk, an independent.

Zbidi had held the defense portfolio since shortly after Tunisia's January 2011 popular revolution that ousted veteran dictator Zine al-Abidine Ben Ali. Under Zbidi, the military helped keep public order while staying out of politics.

Tunisia plunged into political crisis a month ago when the assassination of secular opposition politician Chokri Belaid ignited the biggest street protests since Ben Ali's overthrow.

Ennahda denied any part in Belaid's killing but secularists had long complained that Jebali's government was too tolerant of Islamist radicals suspected to be behind the attack. Ben Ali's regime spent decades suppressing Islamists.

The new government will be under intense pressure to tackle high unemployment, raise wages and revive economic growth.

The so-called Jasmine Revolution in 2011 was the first of several Arab uprisings. Tunisia's political transition has been more peaceful than those in neighboring Egypt and Libya, but tensions are festering between Islamists elected to power and liberals who fear the loss of hard-won liberties.

While Islamists played no major role in the Tunisian revolt, the struggle over Islam's role in government and society has emerged as one of the most divisive political issues.

(Reporting By Tarek Amara; Editing by Mark Heinrich)