UN Secretary General Ban Ki-moon and ambassadors from the United States, Britain, France, Russia and China have discussed "possible diplomatic moves to end" the Syria conflict.
UN diplomats have reportedly said that peace envoy Lakhdar Brahimi was determined to quit.
They said Mr Brahimi wanted to resign from the joint UN-Arab League role because he is frustrated with international deadlock over how to end Syria's two-year civil war, which has killed 70,000.
UN diplomats have also floated the idea of a "Geneva 2" summit.
This would revisit an agreement by world powers in Geneva in June last year that said a transitional government should be formed in Syria "on the basis of mutual consent."
The envoys from the permanent five veto-wielding members of the UN Security Council declined to comment after meeting with the secretary general.
A dispute between Russia and the United States over Syria has left the council paralyzed.
Mr Brahimi, appointed last year after Kofi Annan resigned as Syria mediator, also wants to distance himself from the Arab League, envoys said, because of its decision to recognise Syria's opposition.
Meanwhile, US Defense Secretary Chuck Hagel said the United States was rethinking its opposition to arming the Syrian rebels.
It carries the risk of arms finding their way into the hands of anti-American extremists among the insurgents, such as the al-Nusra Front.
However, it is viewed to be preferable to many in the US rather than direct US military intervention in the conflict.
Arming the opposition is also viewed in the US as preferable to establishing a no-fly zone or sending in troops to secure chemical weapons.
Asked whether the Obama administration was rethinking its opposition to arming the rebels, Mr Hagel said: "Yes."
Pressure on Mr Obama to act on Syria has grown since the disclosure of US intelligence that President Bashar al-Assad's forces likely used chemical weapons on a small scale, particularly sarin gas.
The Syrian government has also mounted a string of attacks reaching from the capital, Damascus, and the central city of Homs out to the Mediterranean coast, homeland of the Alawite minority sect to which Mr Assad himself belongs.
Forces loyal to Mr Assad stormed the coastal village of Baida yesterday, killing at least 50 people, including women and children, the Syrian Observatory for Human Rights said.
The conflict has cost more than 70,000 lives and forced refugees to flee to US allies Turkey and Jordan.