If Syria acquired some of Saddam's WMD while the UN was stalling and slowing the US led toppling of Saddam, the UN is responsible for proliferating these WMD's to Syria.
1. The Syrians cannot repel either an Israeli or a US attack.
2. Their Arab friends will be of no help at all.
3. They saw the pictures of Saddam getting his "checkup".
4. They owe us money.
So, what are they mouthing off for? It would almost appear that they are squealing on themselves. I think its let's make a deal time.
Or an even simpler option : Syria has no WMDs (except mustard gas and the likes), but knows Israel has nukes. So Syria says : let's negotiate for a nuclear-free Middle-East, Israel gets rid of his nuclear arsenal and we get rid of our mysterious WMDs...Of course, that does not affect Syria as much as it would affect Israel, should Syria plan a fifth Israel-Arab war. Given the regional demographics, Israel needs to keep the nukes, while Syria's defense (or even attack) power is largely unaffected by the destruction of chemical warheads.
It reminds me of the trick played on the Soviets by the Reagan administration. The United States told Russia they were ready to begin another round of negotiations for the global reduction of armed forces, EXCEPT for the "Star Wars" program. Russia panics, because they see this as the proof that the United States are ready to deploy a fully operational antimissile satellite grid. Russia does not have the money to build its own system, and gives more than intended in the negotiations.
I think Syria has an empty hand, but tries to win the game nonetheless...