Erdoğan has been one of Syrian President Bashar al-Assad's harshest critics, accusing him of creating a "terrorist state", allowing the Syrian opposition to organise on Turkish soil, and pushing for a foreign-protected safe zone inside Syria.
Washington sees Turkey as the key player in supporting Syria's opposition and planning for the post-Assad era, but Ankara has found itself increasingly isolated and frustrated by a lack of international consensus on how to end the chaos.
"The main source of disappointment is Russia. Let alone raising its voice against Syria, it stands by the massacre," Erdoğan said in an interview broadcast live on Turkish television station NTV.
"China stands by Russia, and although [Chinese President] Hu Jintao had told me they wouldn't veto the plan [for a safe zone] for a third time, they did at the UN vote," Erdoğan said.
He described Iran's position on the 18-month-old uprising against Assad as "impossible to understand".
World leaders meeting at the United Nations this week have expressed concern at the continuing violence in Syria but remain deadlocked over their response.
The United States, European allies, Turkey and Gulf Arab states have sided with the Syrian opposition while Iran, Russia and China have backed Assad, whose family and minority Alawite sect have dominated Syria for 42 years.
Protection for rebel-held areas in Syria would require no-fly zones enforced by foreign aircraft, which could stop deadly air raids by Assad's forces. But there is little chance of securing a Security Council mandate for such action given the opposition of veto-wielding members Russia and China.
China insists any solution to Syria's crisis must come from within the country, while Russia has said many Syrians still support Assad.
Erdoğan had been due to travel to New York to join the UN General Assembly meetings but cancelled his trip at the last minute. Officials cited a heavy work schedule ahead of a key ruling party congress on Sunday, but some observers said it was a sign of frustration at the international deadlock.
The violence in Syria is spiralling as Assad responds to rebel military gains with air strikes and artillery bombardment, killing hundreds every day and sending close to 300,000 refugees into neighbouring Jordan, Iraq, Lebanon and Turkey.
"Assad's days are numbered," Erdoğan said. "He may have to leave soon, he can't resist this anymore."