Israel will act if Syria passes chemical weapons into Hezbollah's hands, Israeli ambassador to Washington Michael Oren warned on Sunday.
"We have a very clear red line about those weapons passing into the wrong hands," Oren told Fox News.
"Were those weapons to pass into the wrong hands, into Hezbollah's hands for example, that would be a game changer for us." Armed with chemical weapons and a large cache of rockets, Oren said, the terrorist group could kill "thousands of people."
Syria has one of the world’s largest chemical weapons arsenals, according to Leonard Spector, executive director of the James Martin Center for Nonproliferation Studies based in Washington. Syria’s arms cache includes “traditional chemical agents, such as mustard, and more modern nerve agents, such as sarin, and possibly persistent nerve agents, such as VX,” he told the BBC on Tuesday.
While Damascus has never confirmed that it has chemical weapons, it has insisted that it would never use them against its own people.
The Israeli red lines differ from those set by US President Barack Obama, who issued a warning to Syrian President Bashar Assad on Monday not to use such weapons against opposition forces.
"The use of chemical weapons is and would be totally unacceptable and if you make the tragic mistake of using these weapons, there will be consequences and you will be held accountable," Obama said.
Noting strong cooperation between Israel and the US on the issue, Oren said "We support the (US) president's red lines as well."
Addressing the presence of al-Qaida elements in the Syrian opposition, Oren said, "The jihadi presence is big and getting bigger, and the longer the conflict goes on there, the bigger it will get."
US Ambassador to Syria Robert Ford warned on Thursday that extremists were gaining influence in the Syrian opposition, saying such groups had “little by little been gaining influence among the armed opposition.”
Extremist elements, which are still a minority among the opposition, pose “an obstacle to finding the political solution that Syria needs,” he said.
On Saturday, British Foreign Secretary William Hague said he has seen "some evidence" that Assad's regime is
preparing to use chemical weapons against the rebels, AFP reported.
"We have seen some evidence of that," Hague said to reporters in Manama at a regional security conference.
"We and the US, as I said in parliament this week, have seen some evidence of that and that is why we have issued strong warnings about it. We have done so directly to the Syrian regime," AFP quoted him as saying.
Sources in Iraq say Assad’s inner circle is engaged in “intensive debate” between those who
advocate using chemical weapons as a last resort and those who warn of the dangers of such a step, Kuwaiti daily
Al-Seyassah reported on Thursday.
US intelligence officials also intercepted one communication within the last six months they believe was from the Iranian Revolutionary Guard Corps’s elite extraterritorial unit, the Qods Force, according to the Washington Post. That communication reportedly urged Syrian regime members to use its supplies of Sarin nerve gas against rebels and the civilians supporting them in Homs.
Tehran, which has much to lose if Assad falls, has been accused by the US in the past week of continuing to ship arms to the Syrian regime via Iraqi airspace. The Syrian opposition has also accused the Revolutionary Guards of providing military assistance to Assad.
Joana Paraszczuk, Hilary Leila Kreiger and Reuters contributed to this report.