World powers traded blame on Thursday after Kofi Annan quit as international peace envoy to Syria, complaining that his initiative to end the bloodshed there never received the support it deserved.
As Syria's government deployed fighter jets against rebels armed with tanks around the commercial capital Aleppo, the outgoing UN-Arab League envoy voiced regret at the "increasing militarisation" of the nearly 17-month conflict.
He hit out at "continuous finger-pointing and name-calling" at the UN Security Council, which he said had prevented coordinated action.
"I did not receive all the support that the cause deserved," Annan told a hastily arranged news conference in Geneva.
Annan's resignation sparked a new round of recriminations among the council's five permanent members, with the United States blaming Russia and China for vetoing three separate UN resolutions on the conflict.
"Annan's resignation highlights the failure at the United Nations Security Council of Russia and China to support meaningful resolutions against Assad that would have held Assad accountable," said White House spokesman Jay Carney.
Germany also said Annan's decision was partly due to Chinese and Russian opposition to sanctions. But Russia's envoy to the world body insisted Moscow had supported Annan "very strongly," and Putin called his resignation a "great shame".