BEIRUT (AP) — The leader of Lebanon’s Hezbollah militant group vowed to help propel President Bashar Assad to victory in Syria’s bloody civil war, warning that the fall of the Damascus regime would give rise to extremists and plunge the Middle East into a “dark period.”

In a televised address, Sheikh Hassan Nasrallah also said Hezbollah members are fighting in Syria against Islamic radicals who pose a danger to Lebanon, and pledged that his group will not allow Syrian militants to control areas along the Lebanese border. He pledged that Hezbollah will turn the tide of the conflict in Assad’s favor, and stay as long as necessary to do so.