The sources told Reuters that Hezbollah had not yet been asked to intervene, adding that the group was not ready to send forces to Syria at this stage following more than a year of hostilities against the Israeli military, including two months of heavy ground fighting in southern Lebanon.

Lebanon's Hezbollah, long the most capable Iran-backed force on the battlefield and key to Assad's military alliance in Syria, has not yet been asked to intervene and was not ready to send forces after its gruelling conflict with Israel, said three sources familiar with the group's thinking.

The loss of Aleppo to Islamist rebels represents a stunning defeat for the Syrian regime, highlighting its dependence on enfeebled allies.

The Lebanese Hezbollah movement, which played a crucial role in defending the Syrian government throughout the neighboring country's civil war, has told Newsweek that the redeployment of its fighters would not be necessary in the face of a new large-scale rebel offensive.

The sources told Reuters that Hezbollah had not yet been asked to intervene, adding that the group was not ready to send forces to Syria at this stage following more than a year o