France has contributed $1.2 million to the Syria mission of global watchdog the Organisation for the Prohibition of Chemical Weapons.
This came a week after the UN disarmament chief reported the discovery of an undeclared chemical warfare agent at a Syrian site to a UN Security Council meeting.
Last month, Syria was stripped of its voting rights by OPCW member states after its forces were found to have repeatedly used poison gas during the country's civil war.
France's voluntary contribution, announced on Monday, was formalised by its representative to the OPCW, Luis Vassy, and the intergovernmental group's director general, Fernando Arias.
At the UN meeting, the US and its Western allies clashed with Russia over international findings that Syria has used chemical weapons.
UN High Representative for Disarmament Affairs Izumi Nakamitsu did not name the agent detected in samples by the OPCW.
But she said its presence “inside storage containers of large volume at a previously declared chemical weapons facility may imply undeclared production activities”.
Syria joined the Chemical Weapons Convention in September 2013, pressed by its close ally Russia, after a deadly chemical weapons attack that the West blamed on Damascus.
By August 2014, President Bashar Al Assad's government declared the destruction of its chemical weapons was complete.
But Syria's initial declaration of its chemical stockpiles and chemical weapons production sites to the OPCW is disputed.
Ms Nakamitsu told the council that Syria reiterated recently that a former chemical production facility was never used to produce or weaponise chemical weapons.
The OPCW had said information and materials gathered there since 2014 indicated “that production and/or weaponisation of chemical warfare nerve agents did, in fact, take place at this facility”.
Ms Nakamitsu said the OPCW rejected Syria's latest denial and still maintains that the Assad regime must declare all chemical warfare agents produced at the site.
