Fears are rising in the West after reports that Bashar al-Assad might be ready to use Syria's chemical weapon arsenal to save his embattled regime, although experts caution against speculation.
On Monday, Nawaf Fares, who defected from his post as Syrian ambassador to Iraq, said in an interview with the BBC that he was "convinced" that Assad would draw on his stocks if cornered.
His comments were backed up by members of the rebel Syrian Free Army.
A few days earlier, the Wall Street Journal said that intelligence reports suggested some chemical weapons were on the move, although the reasons were unclear.
It said some US officials feared the weapons could be used against rebels or civilians, while others believed they were being deliberately hidden from armed opposition groups or Western powers.
There is also concern that the weapons could pass into the hands of groups like Al-Qaeda.
Both Fares and the Syrian Free Army even allege that chemical weapons have already been used during the Syrian conflict.
In reality, very little is known about Syria's chemical capabilities as the country is not a member of the Organisation for the Prohibition of Chemical Weapons, which requires member states to be transparent and destroy their stockpiles.
"The information available is extremely tenuous and often contradictory," said one Western diplomat, speaking on condition of anonymity.
"We don't know (Syria's) calculation, it's something we're imputing from the outside," said Daniel Byman, an analyst at the Brookings Institution in Washington.
The secrecy surrounding the stockpiles has rattled Israel, which believes it could be a direct target.
Israel's deputy chief of the general staff, Major General Yair Naveh, said in June that Syria has the "biggest chemical weapons arsenal in the world."
"(Syria) has missiles and rockets capable of reaching any part of Israeli territory," he warned.
Syria has, however, never used chemical weapons against Israel, even during the 1982 Lebanon war.
Syria is believed to have stockpiles of the deadly nerve agent sarin gas, as well as reserves of cyanide and of mustard gas, which was used in World War One.
Its programme is thought to be "quite large", said Byman.
Experts think the programme has been developed over the last 40 years, initially with help from the former Soviet Union in a bid to reinforce Syria's capacities against Israel then later by Iran.
According to a 2008 report from the Centre of Strategic and International Studies (CSIS), Iran helped Syria build production centres and provided equipment.
"There are reports that Syria has benefited from sales and technology transfers from Iran," CSIS said.
Another study by the California-based Centre for Nonproliferation Studies showed that Syria has four or five chemical weapons factories near to the capital Damascus, the second city of Aleppo and in the province of Hama, one of the flashpoints of the conflict.
Syria reportedly organised military exercises in early July, say experts, including practice firing of Scud and SS-21 missiles that can be used to deliver chemical weapons.
But actually employing these missiles would be hugely risky for Assad, said Bynam.
"If (Syria) uses these things, it would kill people (...) and it has a huge diplomatic cost.
"It would be very, very risky, so the general view is that the regime would only use it if it were about to collapse," leading most probably to serious intervention from the West, he said.
Neighbouring Jordan's King Abdullah II also said that in the event of a descent into all-out war chemical arms could fall into extremist hands, including those of rebel groups.
"Our information is that there is a presence of Al-Qaeda in certain regions inside Syria, and has been there for a while," he told CNN Wednesday.
"And, again, one of the worst-case scenarios as we are obviously trying to look for a political solution would be if some of those chemical stockpiles were to fall into unfriendly hands," he warned.
"As it comes to chemical weapons falling into rebel hands, I think at the end of the day all of us would suffer from that."
The United States said last Friday that Syrian officials would be "held accountable" if they failed to safeguard the country's chemical weapons in one place.