The UN-Arab League joint special envoy to Syria, Kofi Annan has announced he is leaving his post.In a news conference, he said the Syrian people "desperately need action" but criticised the UN Security Council for "finger-pointing and name-calling".Mr Annan authored a six-point peace plan for Syria which was intended to bring an end to the fighting.But the plan was never fully adhered to by either side and the violence has continued to escalate.UN Secretary General Ban Ki-moon said it was "with deep regret" that he announced Mr Annan would not renew his mandate when it expires at the end of August.The Syrian foreign ministry also expressed regret at the announcement, state TV reported.Speaking in Geneva, Mr Annan said the increasing militarisation of the Syrian conflict and the "clear lack of unity" in the Security Council had "fundamentally changed the circumstances for the effective exercise of my role".He said the problems were "compounded by the disunity of the international community”.Russia and China have vetoed resolutions on the crisis three times, citing opposition to any action which might be seen as regime change imposed from outside."When the Syrian people desperately need action, there continues to be finger-pointing and name-calling in the Security Council,” he said."It is impossible for me or anyone to compel the Syrian government, and also the opposition, to take the steps to bring about the political process."Syria can still be saved from the worst calamity - if the international community can show the courage and leadership necessary to compromise on their partial interests for the sake of the Syrian people - for the men, women and children who have already suffered far too much.”Mr Annan said he did not rule out someone taking over the mediator’s role from him, but said a successor might choose another path.He said the focus remained on political transition, as President Bashar al-Assad "will have to leave sooner or later”.In his statement, Mr Ban said he was in discussion with the Arab League to find a successor to "carry on this crucial peacemaking effort”.He said Mr Annan deserved "profound admiration” for the way he had tackled "this most difficult and potentially thankless of assignments” and that he remained convinced bloodshed would only bring "deeper suffering to the country and greater peril to the region”.