http://www.bbc.co.uk/news/world-middle-east-24516303
He told the BBC he hoped the Nobel Peace Prize, awarded to the group last week, would help their work in Syria.
Syria officially joins the Chemical Weapons Convention on Monday.
He said they had been taken wherever they wanted to go, and that they had already reached five out of at least 20 facilities capable of producing chemical weapons.
However, Mr Uzumcu said, routes to some of the sites went through opposition-held territory and this prevented access.
"They change hands from one day to another, which is why we appeal to all sides in Syria to support this mission, to be co-operative and not render this mission more difficult. It's already challenging," he said.
The head of the body tasked with destroying Syria's chemical weapons says fighting is preventing access to some sites through rebel-held areas.
Ahmet Uzumcu, of the Organisation for the Prohibition of Chemical Weapons, called for local, short-term ceasefires to allow experts to work.He told the BBC he hoped the Nobel Peace Prize, awarded to the group last week, would help their work in Syria.
Syria officially joins the Chemical Weapons Convention on Monday.
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“Start Quote
End Quote Ahmet Uzumcu OPCW director generalThey are working in very challenging circumstances in the field”
The OPCW and the UN have had a team of 60 experts and support staff in Syria since 1 October. They are based in Damascus and have been carrying regular visits to facilities.
In his first interview since the OPCW won the prize, Mr Uzumcu told the BBC's Today programme that Syrian officials had been co-operating and facilitating the experts' work.He said they had been taken wherever they wanted to go, and that they had already reached five out of at least 20 facilities capable of producing chemical weapons.
However, Mr Uzumcu said, routes to some of the sites went through opposition-held territory and this prevented access.
"They change hands from one day to another, which is why we appeal to all sides in Syria to support this mission, to be co-operative and not render this mission more difficult. It's already challenging," he said.
