The chief peace negotiator for Syria's mainstream opposition says he is quitting his post, over the failure of United Nations-backed peace efforts to find a political solution to the country's long running civil war.
Mohammed Alloush, in a statement Sunday, linked his decision to ongoing military violence from government forces seeking -- with Russian help -- to preserve the embattled presidency of Bashar al-Assad.
Writing on Twitter, Alloush -- a senior member of the powerful Jaish al-Islam rebel group -- cited what he described as "the stubbornness of the [Assad] regime and its continued bombardments and aggressions toward the Syrian people."
Two weeks of peace talks in Geneva, where U.N. envoys met separately with envoys from the Assad government and opposition groups, ended in April without a deal, as fighting flared anew near the Syrian border.
A third round of talks tentatively set for late May has failed to materialize. Last week, U.N. special envoy Staffan de Mistura said no date would be set for further negotiations until the warring parties agree to a truce allowing humanitarian aid to reach tens of thousands of increasingly desperate Syrian civilians.
There was no immediate U.N. comment Sunday to Alloush's announced departure.
Analysts earlier this year voiced guarded optimism that the Geneva talks could result in a settlement ending five years of war that has left nearly 300,000 dead and driven millions of others from their homes.
But hopes waned when a temporary cease-fire agreed on in February between the Assad regime and non-jihadist rebels was repeatedly violated.
Fighting also flared near the northern city of Aleppo in mid-April as the Geneva talks opened.