The United States on Tuesday boycotted a session of the world’s leading disarmament body, citing Syria's chairmanship as a bid to normalise Bashar Al Assad's regime, which has been accused of numerous chemical attacks since the outbreak of civil war in 2011.
The decision came on the same day that the US and Turkey brokered a deal for the Syrian Kurdish YPG militia to remove its military advisers from the northern Syrian town of Manbij and a surprise ISIS offensive on eastern Syrian villages left at least 45 pro-regime fighters dead.
The events underscored the fractures, battlelines and conflicting parties that remain in the war-ravaged country, now mired in its eighth year of conflict.
Robert Wood, the US ambassador to the Swiss-based body, explained Washington’s decision as a reaction to the conduct of the government of President Al Assad throughout the civil war.
"Based on Syria's repeated attempts last week to use its presidency of the Conference on Disarmament to normalise the regime and its unacceptable and dangerous behaviour, we are not participating in today's session," Wood said in a statement.
"We will continue to defend United States' interests" in the disarmament body, he added.
The US has played a role in a larger proxy war in Syria, aiding rebels opposed to Al Assad and stationing troops on the ground to aid the fight against ISIS, which captured large swathes of northern and eastern Syria from 2014 onwards.
US President Donald Trump has taken a stronger stance against the Syrian regime’s alleged chemical weapons activity, striking several alleged chemical production sites in April alongside France and Britain.
Syria last week took over the body's rotating, four-week presidency, which according to a decades-old practice among its 65 member states follows the alphabetical order of country names in English.
Mr Wood was present during the first plenary session on Syria's watch a week ago, when he took the opportunity to lead a number of countries to protest what he described as "a travesty".
Syria's ambassador Hussam Edin Aala meanwhile slammed last week's protest as "sensational propaganda" and "characterised by double-standards".
More than 350,000 people have been killed and millions displaced since Syria's civil war began in 2011 with the brutal repression of anti-government protests.
After hundreds of people died in chemical attacks near Damascus in 2013, a deal with Russia was struck to rid Syria of its chemical weapons, staving off US air strikes. But Damascus has since been accused of several mass-casualty chemical attacks.
A suspected chlorine and sarin attack in the Syrian town of Douma that left more than 70 people dead on April 7 this year triggered the punitive missile strikes against by the US, Britain and France.
Elsewhere in Syria, the Syrian Kurdish YPG militia said on Tuesday its military advisers would leave Syria's Manbij, a day after Turkey and the United States reached an agreement for administering the area that includes a longstanding Turkish demand that the YPG withdraw.
The deal has eased fears of a direct clash between NATO allies Washington and Ankara over the strategic northern town once held by ISIS but controlled by Kurdish-Arab forces since August 2016.
Under the roadmap endorsed by Ankara and Washington for Manbij, near Syria's northern border with Turkey, the two nations would jointly maintain security and stability there.
Turkey views the YPG as a terrorist group and an extension of the outlawed Kurdistan Workers Party (PKK), which has waged a three-decade insurgency on Turkish soil in a conflict that has left thousands dead. Washington views the YPG as a key ally in the fight against ISIS.
In a statement, the YPG said its fighting forces had withdrawn from Manbij in November 2016 shortly after ISIS was defeated there, but military advisers which had remained would now also withdraw.
In Washington, U.S. officials welcomed the announcement. "Those advisers are largely there to ensure that if there was a military offensive, they would be there to defend the city," a U.S. official told reporters. "Without the threat of a military offensive, the situation is different".
But the danger to former ISIS-held territory in Syria remains. An offensive by ISIS on several villages in eastern Syria on Tuesday left at least 45 pro-regime fighters dead, according to a monitoring group.
ISIS fighters launched the operation Sunday against Euphrates Valley villages seized last year by government forces and their allies, and have retaken four of them, the Syrian Observatory for Human Rights, a UK-based monitoring group opposed to the Syrian regime, said.
The villages are located on the road between the provincial capital of Deir Ezzor and the city of Albu Kamal, which lies further south on the border with Iraq.
The Observatory said the casualties on the pro-regime side were mostly fighters from Shiite militias present in the area, including groups from Iraq, Afghanistan and Lebanese militia Hezbollah.
The small pockets controlled by ISIS in that area are the last dregs of the sprawling self-styled caliphate the group proclaimed over large parts of Syria and Iraq in 2014.