Radical Islamist cleric Abu Qatada, who is on trial in Jordan for terrorism, called on Muslim extremist groups in Syria Thursday to end their infighting and unite ranks.
"The fighting between Islamist factions should end," he told reporters during his trial in Amman.
"Abu Bakr al-Baghdadi, leader of the Islamic State of Iraq and the Levant (ISIL), should dissolve his group and work under the Nusra Front," he said, referring to orders given by Al-Qaeda leader Ayman al-Zawahiri.
"The two groups should reconcile and focus on fighting those who fight them."
He also called for an "end to kidnappings... You should not kidnap or kill anyone who does not carry weapons to fight you."
A new front in Syria's nearly three-year-old civil war opened in early January, when powerful rebel groups combined to attack ISIL bases.
The jihadists were initially welcomed by other rebels, but allegations of brutal abuses against civilians as well as rival opposition fighters sparked a backlash, and even accusations that they were serving the interests of the regime.
In some cases, Al-Nusra, the officially recognised Al-Qaeda franchise in Syria, participated in fighting against ISIL, but its leader recently called for reconciliation.
Signup to our newsletter and follow us on Facebook and Twitter!
Abu Qatada's remarks came after Al-Qaeda chief Ayman al-Zawahiri ordered the ISIL to stop meddling in Syria and anointed Al-Nusra to carry the network's banner in the civil war.
This week, Abu Muhammad al-Maqdisi, a jihadist ideologue and the ex-mentor of Abu Musab al-Zarqawi, the slain leader of Al-Qaeda in Iraq, echoed similar views.
During his trial, Abu Qatada complained that the "hearings and procedures were too slow," demanding the court "be committed" to a Jordanian-British agreement that led to his deportation from the United Kingdom last summer.
"I came to Jordan because it is a blessed land and I want to die here. You must be committed to the agreement, which has become a law. Otherwise, I will boycott the hearings," he said.
The trial was adjourned until January 30.
The Palestinian-born preacher was condemned to death in absentia in 1999 for conspiracy to carry out terror attacks, including on the American school in Amman, but the sentence was immediately commuted to life imprisonment with hard labour.
In 2000, he was sentenced in absentia to 15 years for plotting to attack tourists in Jordan during millennium celebrations, and videotapes of his sermons were allegedly found in the Hamburg flat of 9/11 ringleader Mohammed Atta.
He has pleaded not guilty to all charges.
After his deportation, Abu Qatada was granted a retrial in line with Jordanian law, and military prosecutors charged him with conspiracy to carry out terrorist acts. If convicted he could face a minimum of 15 years' hard labour.
Britain's expulsion of Abu Qatada came after Amman and London ratified a treaty guaranteeing that evidence obtained by torture would not be used in his retrial and that the proceedings would be transparent.