* Israel fears Syria may hand chemical weapons to Hezbollah
* Clearest indication of Israel's "red line" for action
* No certainty Hezbollah could deploy such weapons
Israel is preparing for a possible military intervention in Syria in case the Syrian government hands missiles or chemical weapons to the Lebanese Islamist movement Hezbollah, Defence Minister Ehud Barak said on Friday.
"I have instructed the military to increase its intelligence preparations and prepare what is needed so that ... (if necessary) ... we will be able to consider carrying out an operation," Barak said in an interview on Channel 10 television.
"We are following ... the possible transfer of advanced munitions systems, mainly anti-aircraft missiles or heavy
ground-to-ground missiles, but there could also be a possibility of the transfer of chemical means (weapons) from Syria to Lebanon," he added.
"The moment (Syrian President Bashar al-Assad) starts to fall we will conduct intelligence monitoring and will liaise with other agencies," Barak said.
Hezbollah, which has in the past received military and financial support from Syria and Iran, launched thousands of mainly short-range rockets into Israel during Israel's 2006 offensive in southern Lebanon, but some longer-range rockets reached central Israel.
Their border has largely remained quiet since then.
On Thursday, Barak toured the Golan Heights, a strategic plateau that Israel captured from Syria in the Middle East war in 1967 and from where it can monitor movements inside the territory of its northern foe.
Barak said Israeli troops were preparing to prevent an influx of refugees into territory that Israel controls there.
"They (refugees) have not chosen to come close to us, but in the event of the regime's downfall, which could happen..., (Israeli forces) here are alert and ready, and if we have to stop waves of refugees, we will stop them," Barak said.
Syrian rebels have assassinated four of Assad's closest aides in Damascus and seized three border crossings with Iraq and Turkey this week, putting the Syrian leader under greater pressure than at any time in the 16-month uprising against his rule.