"Increasing tensions and the inability to reach a compromise in the establishment of an accountability mechanism (for chemical weapons use in Syria) threaten to lead to a full-blown military escalation," Guterres told the Security Council on Friday, Xinhua news agency reported.
"In my contacts with you -- especially with the permanent members of the Security Council -- I have been reiterating my deep concerns about the risks of the current impasse and stressed the need to avoid the situation spiralling out of control. This is exactly the risk we face today -- that things spiral out of control," said the UN chief.
"It is our common duty to stop it."
"In Syria, we see confrontations and proxy wars involving several national armies, a number of armed opposition groups, many national and international militia, foreign fighters from everywhere in the world, and various terrorist organisations," he told the Security Council, which was convening at the request of Russia.
"From the beginning, we have witnessed systematic violations of international humanitarian law, international human rights law, and international law tout court -- in utter disregard of the letter and spirit of the United Nations Charter."
For eight years, the people of Syria have lived through a litany of horrors: atrocity crimes, sieges, starvation, indiscriminate attacks against civilians and civilian infrastructure, the use of chemical weapons, forced displacement, sexual violence, torture, detention and enforced disappearances, he said.
The continued reports of chemical weapons use in Syria are outrageous, he said. He deplored the fact that the Security Council could not reach agreement on a dedicated mechanism for attributing accountability in this regard.
"I reiterate my strong condemnation of the use of chemical weapons by any party to the conflict and under any circumstances. Their use is abhorrent and a clear violation of international law."
The seriousness of the recent allegations of a chemical attack in Douma, Syria, requires a thorough investigation using impartial, independent and professional expertise, he said.
The OPCW mission should be granted full access, without any restrictions or impediments to perform its activities, he said.
Guterres urged the Security Council, which failed to adopt a resolution on Tuesday on a new investigative mechanism for chemical weapons use in Syria, not to give up on its efforts to agree upon a "dedicated, impartial, objective and independent mechanism" for attributing responsibility.
He stressed that there is no military solution to the Syrian conflict. "The solution must be political through the Geneva intra-Syrian talks."
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