PEACE in our time or a cynical diplomatic fudge? The best that can be said of the provisional agreement on a “cessation of hostilities” between at least some of the warring parties in Syria, hammered out (again) on February 22nd between John Kerry, America’s secretary of state, and Sergei Lavrov, his Russian opposite number, is that it appears to have slightly more solid foundations than a similar attempt earlier this month.

The agreement, which is due to come into force on February 27th, was endorsed by Vladimir Putin in a rare television address after he conferred by telephone with Barack Obama. As The Economist went to press, details of how it would be implemented were still being worked through. It looks likely that at least one of the requirements of the UN peace plan outlined by the UN Security Council late last year may be fulfilled: the lifting of sieges of rebel-held towns by government forces and the delivery of humanitarian aid to their starving populations. Some aid convoys began to roll from Damascus last week and more will follow. Bashar al-Assad, Syria’s president, has also promised to hold (meaningless) parliamentary elections on April 13th. Just about everything else remains unclear.

The Russians have given themselves and Mr Assad plenty of latitude in the way they wish to interpret the agreement. The Syrian regime refuses to describe it as a ceasefire, instead referring to a mere suspension of combat operations. In practice, it may not even amount to that.

Islamic State (IS) and Jabhat al-Nusra (JAN), al-Qaeda’s Syrian affiliate, are officially designated as terrorist groups by both Moscow and Washington, and are thus explicitly excluded from the agreement. But JAN, intermingled with other rebel groups, is active on almost every front in the civil war, from Daraa in the far south of the country to Aleppo in the north. JAN is also the leading player in a rebel alliance that includes Ahrar al-Sham, a powerful Salafist outfit, and other less extreme groups. It controls most of Idlib province to the west of Aleppo. Having largely completed the encirclement of Aleppo, the regime’s next priority is to cut off and squeeze Idlib. Fabrice Balanche of the Washington Institute for Near East Policy argues that if Russia continues air strikes against JAN, as the agreement entitles it to, it will be impossible for other groups fighting alongside it to respect the ceasefire.