United Nations and Arab League special envoy to Syria Kofi Annan on Thursday urged the Syrian opposition to cooperate to resolve the conflict that has left thousands dead in the past year.

Former UN chief Annan, speaking to reporters in Cairo, urged "the Syrian opposition to come together to work with us to find a solution that will respect the aspirations of the Syrian people."

Annan was in Cairo for talks with officials ahead of a trip to Damascus on Friday.

"We will do whatever we can to urge and press the cessation of hostilities and an end to the killing and violence," he said ahead of talks with Foreign Minister Mohammed Amr.

"But of course the ultimate solution lies in the political settlement," Annan said.

More than 7,500 people have been killed in an almost year-long crackdown by Syrian forces of protests against President Bashar al-Assad's regime, the United Nations says, and world pressure has been growing for an initiative to end the bloodshed.