Kofi Annan
Kofi AnnanReuters

Former UN Secretary General Kofi Annan has resigned from his post as the UN-Arab League peace envoy for Syria, UN Secretary General Ban Ki-moon said on Thursday. Annan has asked that his mandate not be renewed when it expires August 31. Annan blamed "fingerpointing and name calling" at the U.N. Security Council for his decision to resign.

The White House blamed Kofi Annan's resignation as special U.N. envoy to Syria on the failure of Russia and China to back his peace plan for the violent conflict there, the Associated Press reported.

White House press secretary Jay Carney praised Annan's efforts, but noted that the Syrian government was never willing to embrace the envoy's plan, which included declaring a cease-fire and allowing international monitors to operate in the county.

Russian President Vladimir Putin said he regrets Annan's resignation, Russian news agency Interfax reported. "Kofi Annan is a very respectable person, a brilliant diplomat and a very decent man, so it's really a shame," said Putin, who is in London. "But I hope that the international community's efforts aimed at ending the violence will continue."

Annan said earlier this week he feared an "imminent battle" for Syria's biggest city Aleppo. Syrian opposition sources said helicopters from President Bashar al-Assad's military pounded a rebel-held part of the city on Saturday and armored units were positioned for an onslaught that could determine its fate.

"I am concerned about reports of the concentration of troops and heavy weapons around Aleppo, in anticipation of an imminent battle," Annan said in a statement. "The escalation of the military build-up in Aleppo and the surrounding area is further evidence of the need for the international community to come together to persuade the parties that only a political transition, leading to a political settlement, will resolve this crisis."