Former UN secretary-general Kofi Annan on Thursday was appointed the joint United Nations-Arab League envoy on the Syrian crisis with a mandate to bring an end to the violence and promote a peaceful political solution.

Annan's successor, Secretary-General Ban Ki-Moon, and Arab League Secretary-General Nabil Elaraby announced the appointment ahead of Friday's major international conference on Syria in Tunisia's capital.

The announcement said that as the UN-Arab League special envoy, Annan will work on bringing an end to "all violence and human rights violations, and promoting a peaceful solution to the Syrian crisis."

The statement said Annan will work with parties inside and outside Syria to end the violence and the humanitarian crisis and facilitate "a peaceful Syrian-led and inclusive political solution that meets the democratic aspirations of the Syrian people through a comprehensive political dialogue between the Syrian government and the whole spectrum of the Syrian opposition."

A deputy for the joint special envoy will be chosen from the Arab region, they said.

Diplomats said Thursday that Ban couldn't find a high-level Arab acceptable to both sides and turned to Annan and former Finnish President Martti Ahtisaari as possible candidates.

Both are veteran mediators — Annan in Kenya and Ahtisaari in Kosovo — and both are Nobel Peace Prize winners.

Last week, the UN General Assembly asked Ban to support the Arab League's efforts to promote a peaceful solution to the crisis, including through appointment of a special envoy to Syria.

The focus of the meeting was Syria and the way forward in implementing the General Assembly Resolution including the appointment of a Special Envoy.

They also discussed the humanitarian crisis in Syria and the planned mission of the Under-Secretary-General for Humanitarian Affairs, Valerie Amos, to the country.

Ban met Elaraby, European Union foreign policy chief Catherine Ashton, and Organization of Islamic Cooperation Secretary-General Ekmeleddin Ihsanoglu on the sidelines of a conference on Somalia in London Friday to discuss Syria, the appointment of a special envoy and the planned mission of UN humanitarian chief Valerie Amos to the country, the UN said.

Diplomats, speaking on condition of anonymity because talks were private, said the choice of Annan as joint special envoy was finalized at that meeting.

Annan, 73, served as the UN's secretary-general from 1997 to 2006, leaving behind a global organization far more aggressively engaged in peacekeeping and fighting poverty but struggling to restore its reputation after the scandal over the UN-run oil-for-food program for humanitarian relief in Iraq.

He helped preside over a decade that saw the world unite against terrorism after the Sept. 11, 2001, attacks, then divide deeply over the U.S.-led war against Iraq which toppled Saddam Hussein. He spurred world leaders to adopt a blueprint to wage a global war on poverty and issued a call to action to address the HIV/AIDS pandemic.

After leaving the UN, Annan was immediately suggested as a candidate to be president in his native Ghana, which he turned down. But he has remained active with several African and international organizations.

In 2008, he participated in negotiations to end civil unrest in Kenya following disputed elections and mediated agreement on a coalition government.