
Nusra's resurgence could undermine the Western-backed rebel groups that signed up to the truce and attended the peace talks, and gives Assad's government and its Russian and Iranian backers more reasons to press on with a war during which they have hit insurgents of all stripes. In the latest expansion of its profile, it and other groups have revived the Jaish al-Fatah, or the army of conquest, a military alliance of disparate Islamist rebel groups that won big victories against government forces last year.

After lying low in the early days of the truce, Nusra has re-emerged on the battlefield as the diplomacy has unraveled, spearheading recent attacks on pro-government Iranian militias near Aleppo, Nusra commanders and other rebels say.

The talks broke up last month, with Assad's government and foes blaming each other for military escalation.

Al Qaeda's Syrian branch, the Nusra Front, was excluded from a ceasefire put in place in February and from peace talks that followed. By Tom Perry and Suleiman Al-Khalidi BEIRUT/AMMAN (Reuters) - Jihadi militants in Syria including al Qaeda are mobilizing again for all-out war against President Bashar al-Assad, taking advantage of the collapse of peace talks to eclipse nationalist rival insurgents that signed on to a faltering truce.
