China welcomed the appointment of former UN leader Kofi Annan as a special envoy on Syria on Friday, a day after saying it would not attend an international summit to try to end the violence there.

China's foreign ministry said it hoped Annan's appointment as international troubleshooter for the United Nations and the Arab League would be "conducive to the political resolution of the Syrian issue".

Beijing, which has a long-held policy of non-interference in other countries' affairs, has been strongly criticised for joining Russia in vetoing two UN Security Council resolutions on the crisis in Syria.

Asked at a regular briefing in Beijing about the decision to boycott the Friends of Syria meeting in Tunis, foreign ministry spokesman Hong Lei said China wanted to "play a constructive role" in resolving the issue.

"At the same time, China believes that the international community's efforts should be conducive to alleviating the tensions in Syria, promoting peace and stability in the Middle East, promoting political dialogue and dissolving differences," he said.

The UN and Arab League said Annan would "provide good offices aimed at bringing an end to all violence and human rights violations, and promoting a peaceful solution to the Syrian crisis".

US Secretary of State Hillary Clinton and foreign ministers from Britain, France and Arab countries were expected to extend their support to Annan at the Friends of Syria meeting on Friday, which neither Russia and China will attend.

More than 7,500 people have been killed in 11 months of protests against President Bashar al-Assad in Syria, activists say, and there is growing international pressure for an initiative seeking to end the deadly crackdown.