World must ready to act on Syria chemical arms

The international community must be ready to use military action in response to any chemical weapons use by the Syrian regime, Israel's deputy foreign minister said on Friday.

"From the moment the international community understands that red lines have been crossed and that chemical weapons have been used, they will realise there's no other choice than to react (militarily)," Zeev Elkin told Israeli army radio.

"It's clear that if the US and the international community wish to, they can react militarily and take control of Syria's chemical weapons arsenal," Elkin added.

"This will put an end to all concerns," he said.

The US said Thursday for the first time that Syrian President Bashar al-Assad's regime had likely used chemical weapons against rebel forces, but stressed that intelligence services were not yet 100 per cent sure.

"Our intelligence community does assess with varying degrees of confidence that the Syrian regime has used chemical weapons on a small scale in Syria," US National Security Council spokeswoman Caitlin Hayden said.

A senior US adminstration official said "all options are on the table" if it is confirmed that Syria has used chemical weapons.

The official recalled that the United States is already engaged in "diplomatic initiatives (and) assistance to the opposition" in Syria, where the UN says a grinding civil war has killed more than 70,000 since March 2011.

Last month, during a visit to Israel, US President Barack Obama said the use of chemical weapons would be a "game changer."

Mounting evidence of chemical weapons attacks on fighters battling Assad's regime could increase the pressure on Obama -- who has sought to avoid any US military role in the conflict -- to intervene.

The Pentagon has already sent more than 200 troops to Jordan to prepare for a possible joint operation with allies to secure chemical weapons.

The Israeli army said on Tuesday that Damascus had used chemical weapons, as US Defence Secretary Chuck Hagel wrapped up a three-day visit to Israel.

"To the best of our professional understanding, the (Assad) regime has made use of deadly chemical weapons against the rebels in a number of incidents in the last few months," said Brigadier General Itai Brun, head of the research and analysis division of military intelligence.

"Which chemical weapons? Apparently sarin. The regime is also using chemical weapons that neutralise and are not fatal," he added.

Developed as a pesticide in Germany in 1938, sarin is a deadly and volatile nerve agent that is colourless and odourless.

Washington also fears the Syrian chemical weapons arsenal could fall into the hands of Lebanese Shiite movement Hezbollah, or hardline Islamist groups that are playing an increasingly decisive role in the two-year conflict.