Al Qaeda leader Ayman al-Zawahri urged Syrians to unite to bring down President Bashar Assad and thwart what he said were U.S. plans to set up a client state in Syria to safeguard Israel's security.
The recording was 22 minutes long and posted on an extremist website on Thursday, as Palestines marked the end of the 1967 ear and 65 years since Israel's founding.
During the message, Zawahri said the only way to resolve the Palestinian problem was by waging jihad.
"There is no solution for Palestine except Jihad," Zawahri said.
"America, its agents and allies want you to shed your blood and the blood of your children and women to bring down the criminal Baathist regime, and then set up a government loyal to them and to safeguard Israel's security," he added.
Zawahri's recording was released one day after troops loyal to Syrian President Bashar Assad and Lebanese Hezbollah troops gained control of the Syrian city of Qusair, in the Homs province.
His statement appeared on the Mujahideen al-Ansar website, which carries statements from al Qaeda leaders, Reuters reported.
The recording made no reference to the taking of Qusair, which would indicate that it was made before the offensive began.
Zawahri, an Egyptian-born preacher who became al Qaeda's leader after Osama bin Laden was killed in by the U.S. in 2011, criticised Iran for supporting the Syrian regime, saying the conflict in Syria had "revealed the ugly face of Iran."
Hezbollah, which receives backing from Iran, was crucial in securing the success of Assad's troops in Qusair.
Influential Sunni Muslim cleric Sheikh Youssef al-Qaradawi last week called for Jihad (holy war) against Assad after Hezbollah leader Sheikh Hassan Nasrallah acknowledged his forces had joined the fighting in Qusair, Reuters reported.
He also that the United States wanted to turn the Syrian jihad into a "Western tool against Iran," according to Reuters.
"Every free Muslim in Palestine should unite with his Muslim brothers to implement Sharia (Islamic law) and rule by it, and make it a reference above all references, and to liberate Palestine in order to set up an Islamic state, even if the West hates that and calls it terrorism and extremism," he added in his statement.
