UN leader Ban Ki-moon discussed deadlocked efforts to end the Syria conflict with the major powers on Thursday amid mounting signs that peace envoy Lakhdar Brahimi is to quit.
Diplomats and UN spokesman Martin Nesirky confirmed the meeting but declined to say whether Brahimi has already told the United Nations and Arab League that he would be leaving.
"The decision has been taken, but we don't know when it will be formalized," said one UN diplomat, speaking on condition of anonymity.
A senior aide to the 79-year-old former Algerian foreign minister told AFP no announcement of any resignation was likely to be made until mid-May.
Diplomats say, however, that Brahimi is determined to leave the post.
The permanent Security Council members -- the United States, Russia, China, Britain and France -- have all been urging Brahimi to stay in the position he took up in August after former UN leader Kofi Annan quit, diplomats said.
Brahimi wants to leave out of growing frustration with the stalled international efforts to end the two-year-old conflict, which the United Nations says has killed over 70,000 people.
"People are saying 'we want a political solution' but no one is taking serious steps towards that," said the aide, speaking to AFP in Cairo on condition of anonymity because of the topic's sensitivity.
Brahimi has been criticized by the Syrian opposition, and Assad's government said last week it would no longer cooperate with him.
But the Arab League decision to recognize the opposition Syrian National Coalition as the legitimate government of Syria was the final straw for the veteran UN troubleshooter, diplomats said.
The aide said Brahimi has not yet resigned. "But as you know, he said he thinks about this every day," the aide said.
Ban and the ambassadors from the Security Council's five permanent members meanwhile held informal discussions on Syria, said Nesirky.
"They discussed possible diplomatic moves to end the crisis. He briefed them on the latest developments relating to the chemical weapons investigation mission," said Nesirky.
"They also discussed the ever-worsening humanitarian situation inside Syria," he added.
Britain's ambassador Mark Lyall Grant confirmed to reporters that the peace envoy was discussed at the meeting but added "it was not just about Brahimi."
Brahimi could keep a role as an advisor to the UN secretary general on Syria or the Middle East, according to envoys.
"He will resign and will remain as a special adviser to the secretary general on the Middle East," said the UN diplomat.
"Ban will not rush to appoint a third person," added another Security Council diplomat. "You have had Annan, you have had Brahimi -- are you going to get someone who can do better than them?"