The United Nations and the Arab League have appointed Kofi Annan, a former head of the world body, to act as a joint special envoy on Syria, as international representatives gathered in Tunisia to discuss measures to end the escalating violence in the country.

Ban Ki-moon, the UN secretary-general and Nabil Elaraby, the head of the Arab League, announced the appointment late on Thursday, handing Annan a mandate to bring an end to the violence and promote a peaceful political solution to the crisis.

Al Jazeera's Alan Fisher reports from Washington.