Outgoing UN-Arab League envoy Kofi Annan will not send a representative to a meeting on the Syria conflict to be hosted by Iran on Thursday, a UN spokesman said.

Iran has called a ministerial meeting of states that have taken a "realistic and principled stand" on the Syrian crisis. Iran, a key ally of Syria's President Bashar al-Assad, has said it expects representatives from 10 countries to attend.

"Neither Kofi Annan nor anyone from his office will attend the talks on Syria in Tehran," a UN spokesman, Farhan Haq, told reporters. Haq did not give a reason for the decision.

Annan, who announced last week that he is quitting as Syria envoy because of the lack of international support for his peace plan, went to Iran as part of his mission and had wanted the Iranian government involved in talks on ending the 17-month-old civil war.