Greenpeace's Greek chapter on Wednesday urged more transparency in a UN-led operation to dismantle Syria's chemical arsenal at sea in the eastern Mediterranean to calm fears in nearby coastal communities.

"There is a major communication shortage and the United Nations bears significant responsibility for this," Greenpeace Greece executive director Nikos Charalambides told AFP.

The planned operation to break down the chemicals aboard a US cargo ship in international waters has prompted protests in Italy and Greece despite government assurances that the operation carries no risk to the marine environment.

Syria has declared around 700 tonnes of most dangerous chemicals, 500 tonnes of less dangerous precursor chemicals and around 122 tonnes of isopropanol, which can be used to make sarin gas.

Hydrolysis systems aboard the cargo ship Cape Ray are to mix the chemicals with heated water and other chemicals to break down the lethal agents, resulting in a sludge equivalent to industrial toxic waste.

"At this moment, this is the best possible solution," Charalambides said.

"The sooner the weapons leave Syria, the better for everybody," he said.

However, little information is available on the precise composition and volume of the chemicals involved, Charalambides said.

"The UN has given assurances that nothing will fall into the sea. But will they tell us where (the residue) will ultimately end up?" he asked.

The OPCW held a briefing in January for environmental groups but many details were left unanswered, he said.

Earlier on Wednesday, the head of the OPCW-UN mission to dismantle the arsenal, Sigrid Kaag, said she was confident that a mid-2014 deadline for the regime's entire arsenal to be destroyed would be met.

"Some delays have been encountered, but they have not been insurmountable and we remain confident that the deadline of 30th June 2014 will be met," she told AFP in Damascus.

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