Jabhat al-Nusra, the Syrian branch of al-Qaeda, is a greater threat to Europe and the US in the long term than Isis, according to a new report by the Institute for the Study of War and the American Enterprise Institute.
The report's key findings state: "Jabhat al-Nusra poses one of the most significant long-term threats of any Salafi-jihadi group."
"Its defeat and destruction must be one of the highest priorities of any strategy to defend the United States and Europe from al-Qaeda attacks."
The report argues Isis and Jabhat al-Nusra attacks could threaten the global economy and provoke "Western societies to impose severe controls on... freedoms and civil liberties".
Fred Kagan, one of the authors of the report says Jabhat al-Nusra has made a tactical decision not to attack the West for the time being.
"While Isis is flashier... both represent an existential threat, both wish to attack the homeland, both seek the mobilisation of Muslim communities against the West," he said.
He added: "Al-Nusra is quietly intertwining itself with the Syrian population and Syrian opposition... They are waiting in the wings to pick up the mantle of global jihad once Isis falls."
The report describes how Jabhat al-Nusra has established an extensive network of partnerships with local opposition affiliates which have become fiercely loyal to the organisation.
Jabhat al-Nusra militia group emerged during the early days of the Syrian civil war in 2011, with the aim of establishing an Islamic State in the region.
It recently seized two of Syria's most prominent activists in a raid on their opposition radio station.