UN special envoy Kofi Annan has acknowledged that the international community's efforts to find a political solution to the escalating violence in Syria have failed.
Mr Annan told the French daily Le Monde that more attention needs to be paid to the role of long-time Syrian ally Iran, and added that countries supporting military actions in the conflict are making the situation worse.
He said: "The evidence shows that we have not succeeded."
Mr Annan, the special envoy for the United Nations and the Arab League, is the architect of the most prominent international plan to end the crisis in Syria, which activists say has killed more than 14,000 people since March 2011.
His six-point plan was to begin with a cease-fire in mid-April between government forces and rebels seeking to topple the regime of Syrian president Bashar Assad.
But the truce did not take hold, and now around 300 UN observers sent to monitor the ceasefire are confined to their hotels because of the escalating violence.
Activists reported at least 67 people killed on Friday alone, after some 800 people last week.
Mr Annan defended the unarmed observers, saying it was not their job to stop the violence, but to monitor the sides' adherence to the truce.
He offered few suggestions on how the plan could be salvaged, only saying that Iran "should be part of the solution" and that criticism too often focused on Russia, which has stood by the regime.
"Very few things are said about other countries that send arms and money and weigh on the situation on the ground," he said, without naming any specific countries.
Iran is a long-time Syrian ally and has stood by the Assad's regime throughout the uprising. It is unclear what role Mr Annan envisions for Iran. Tehran's close ties could make it an interlocutor with the regime, though the US has often refused to let the Islamic republic attend conferences about the Syria crisis.
Russia provides the Assad regime with most of its weapons. No countries are known to be arming the rebels, though some Gulf Arab states have spoken positively of doing so. The US and other Western nations have sent non-lethal aid, like communications equipment.
Despite mounting international condemnation, Mr Assad's regime has largely held together. On Saturday, however, France announced the defection of Brigadier General Manaf Tlass, an Assad confidant and the son of a former defence minister who helped ease Mr Assad into power.
Tlass is the highest ranking official to abandon the regime so far, and Western powers and anti-regime activists hoped his departure will encourage others to leave.
News of the defection largely overshadowed an international conference in Paris on Saturday attended by the US, its European and Arab partners and members of Syria's fractured opposition.
The so-called "Friends of Syria" said they would provide means for the opposition in Syria to better communicate among themselves and with the outside world and increase humanitarian aid.
They also called on the UN Security Council to adopt a resolution that would force the regime to comply with the two peace plans that have been largely ignored by both sides in the conflict.
Syrian allies Russia and China would likely veto any resolution seen as too critical of the Syrian government, as they have in the past.