Al Qaeda leader Ayman al-Zawahri slammed US treatment of hunger striking inmates at Guantanamo Bay and said the group would spare no effort to free them, according to an audio recording posted on the Internet on Wednesday.
Zawahri also said Shi'ite Hezbollah's intervention in the conflict in Syria was an attempt to promote Iranian hegemony over the country.
"The (hunger) strike by our brothers at Guantanamo unmasks the true ugly face of (the United States of) America," Zawahri said in an audio recording posted on an Islamist website and whose authenticity could not be verified.
"We pledge to God that we will spare no effort to free all our prisoners, on top of whom are Omar Abdel Rahman, Aafia Siddiqui, Khaled Sheikh Mohammed and every oppressed Muslim everywhere ...," he added, referring to prominent Islamist militants held by the United States.
He did not elaborate on what al Qaeda intended to do, but militants have in the past kidnapped Westerners and sought to trade them for jailed comrades.
Al Qaeda has also claimed responsibility for simultaneous raids on two Iraqi prisons last week in which they said more than 500 inmates had been set free. And in Pakistan, Taliban broke 250 prisoners out of a jail on Tuesday.
Some 166 men, most of whom were rounded up in counter-terrorism operations since the September 11, 2001 attacks on the United States, are currently being held at a US military base in Guantanamo Bay in Cuba.
Many have been on hunger strike to protest their indefinite detention, with some being force-fed. Zawahri also denounced Washington's use of drone strikes targeting Islamists, saying it was a sign of the defeat of US campaigns in Afghanistan, Pakistan and Yemen.
Drone strikes have been widely criticised by rights groups who say the strikes often miss their targets and hit civilians.
"These spying planes will not protect you from defeat, but rather are a sign of your failure and the repeated failure of your government," Zawahri said, addressing US President Barack Obama.
"You are leaving a legacy of hatred and demands for vengeance from you over your crimes," he added.
Zawahri, whose Sunni Muslim network adheres to an austere view of Islam that views Shi'ite Muslims as infidels, also condemned the involvement of Lebanese group Hezbollah in Syria's civil war, singling out its leader Sayyed Hassan Nasrallah.
"It has become clear to the Muslim nation that he (Nasrallah) is but a tool in the Safavid, rejectionist project which seeks to impose the authority of Shi'ite jurisprudence ... on the nation of Islam through slaughter, repression, torture and by supporting one of the most corrupt, tyrannical and criminal regimes," the al Qaeda leader said.