Jihadist rule must spread over Syria after the ouster of Bashar al-Assad, the head of the hardline rebel Al-Nusra Front said on Friday, accusing Washington of seeking to keep the president in power.
Al-Nusra, blacklisted by Washington as a terror outfit, has claimed responsibility for the majority of deadly suicide bombings in Syria's 21-month conflict.
Its fighters, many of whom are foreigners, have also played a major part in battlefield gains made by the rebels in the northwest in recent months.
In an audio tape posted online on Friday the head of the group, Abu Mohammed Al-Jawlani, said clearly - and repeatedly - that Islamists must rule in post-Assad Syria.
"The fall of the regime will leave a vacuum and you are the best placed to fill that void," Jawlani said, addressing his fighters.
Power must go to the "mujahedeen," he said.
In his message, entitled "People of Syria, we sacrifice our souls for you," Jawlani told Syrians: "We have offered you our blood in defending your religion and your lands, and will continue to sacrifice ourselves one after the other.
"We will continue to make sacrifices so that the Syrian people can recover their pride and well-being that have been taken from them, until they can live under the banner [of Islam]... ruled by shura [principles of Islam]," he added.
Jawlani insisted that those who shed their blood in the fight against the regime of Assad, who hails from the minority Alawite community, an offshoot of Shiite Islam, must reap the rewards without foreign intervention.
"This blood which was shed to emerge from oppression... should not be lost in the darkness of the West. He who sows must harvest the fruits," he said.
Jawlani lashed out at the international community, particularly the United States, accused it of seeking to keep Assad in power.
"The continued US and international support for prolonging the regime's lifespan by giving extensions [for a political transition], sending observers and trying to negotiate peace is clear to everyone," the said.
"The United States is expressing its failure in the region by putting the Al-Nusra Front on its terror list [merely] for helping the [Syrian] people," he added.
Washington formally designated Al-Nusra as a "foreign terrorist" organization earlier this month, warning that extremists could play no role in building the nation's future.
Jawlani said the blacklisting had prompted "popular anger among Muslims," including "condemnation from 100 organizations."
The mainstream opposition National Coalition, recognised by Washington as sole legitimate representative of the Syrian people, called on December 12 for a review of the US blacklisting. Al-Nusra is not part of the coalition.
Reacting to Jawlani's message, Middle East specialist Fabrice Balanche told AFP that Al-Nusra has been buoyed by its battlefield successes and was in Syria to stay.
"Al-Nusra did not come to Syria just to pull out once Bashar al-Assad falls," the director of the France-based Gremmo research center said. "Al-Nusra has always been clear about its intentions, they are Salafists and want to set up a caliphate [Islamic state]."
Little is known about Al-Nusra, a jihadist group with roots in Iraq which was officially born last January, according to a video statement distributed online that declared its creation.
Over the months, its role has become ever more prominent on the battlefield, where it has acted as the anti-Assad insurgency's spearhead, while the mainstream rebel Free Syrian Army has struggled to get organized.