Israel is concerned that Syria will transfer anti-aircraft missiles to Hizbullah in Lebanon while the IDF is preoccupied with the escalation in violence in the Gaza Strip, defense officials said on Tuesday. Defense Minister Ehud Barak toured the northern border on Tuesday amid a heightened level of alert, stemming from the fear that Hizbullah might carry out an attack to avenge last February's assassination of arch-terrorist Imad Mughniyeh in Damascus. "It is difficult to know ahead of time where the [Hizbullah] response will come," Barak said. "We are also keeping an eye on the weapons smuggling from Syria to Hizbullah and there are a number of systems that we view as breaking the balance of power that cannot be allowed to be transferred." Israel is specifically concerned that Syria will transfer anti-aircraft systems to Hizbullah. Hizbullah is already believed to have shoulder-to-air missiles and the transfer of additional systems would severely impair the IAF's operational freedom over Lebanon. If these systems are transferred to Hizbullah, Israel would need to "consider its response," Barak said. The Prime Minister's Office's Counter-Terrorism Bureau issued a travel advisory this week, warning all Israelis of a potential Hizbullah attack overseas ahead of the one-year anniversary of the assassination on February 12. Barak said that if there was an attack, Israel would hold the Lebanese government responsible. "Hizbullah is not just a terrorist organization running around the hills but also sits at the cabinet table in Beirut," he said. "Therefore, the Lebanese government bears overall responsibility and any attempt to attack Israel will be met with a response."