BEIRUT: US President Barack Obama urged Russia on Sunday to stop bombing “moderate” rebels in Syria in support of its ally Bashar al-Assad, a campaign seen in the West as a major obstacle to latest efforts to end the war.

Major powers agreed on Friday to a limited cessation of hostilities in Syria but the deal does not take effect until the end of this week and was not signed by any warring parties — the Damascus government and numerous rebel factions fighting it.

Russian bombing raids directed at rebel groups are meanwhile helping the Syrian army to achieve what could be its biggest victory of the war in the battle for Aleppo, the country’s largest city and commercial centre before the conflict.

There is little optimism that the deal reached in Munich will do much to end a war that has lasted five years and cost 250,000 lives.

The Kremlin said President Vladimir Putin and Obama had spoken by telephone and agreed to intensify cooperation to implement the Munich agreement.

But a Kremlin statement made clear Russia was committed to its campaign against the militant Islamic State (IS) group and “other terrorist organisations”, an indication that it would also target groups in western Syria where militants such as Al Qaeda are fighting Assad in close proximity to rebels deemed moderate by the West.

Russia says the “cessation” does not apply to its air strikes, which have shifted the balance of power towards Assad.

It says the IS and the Al Qaeda-affiliated Nusra Fr­o­nt are the main targets of its air campaign. But Western countries say Russia has in fact been mostly targeting other insurgent groups, including some they support.

The White House said Obama’s discussion with Putin stressed the need to rush humanitarian aid to Syria and contain air strikes.

“In particular, President Obama emphasised the importance now of Russia playing a constructive role by ceasing its air campaign against moderate opposition forces in Syria,” the White House said in a statement.

Relief workers said efforts to deliver humanitarian aid were being threatened by the latest escalation of violence.

“We must ask again, why wait a week for this urgently needed cessation of hostilities?” said Dalia al-Awqati, Mercy Corps Director of Programs for North Syria.

The situation in Syria has been complicated by the involvement of Kurdish-backed combatants in the area north of Aleppo near the Turkish border, which has drawn a swift military response from artillery in Turkey.

The Kurdish YPG militia, helped by Russian air raids, seized an ex-military air base at Menagh last week, angering Turkey, which sees the YPG as an extension of the PKK, a Kurdish group that waged a bloody insurgent campaign on Turkish soil over most of the past three decades.

Published in Dawn, February 15th, 2016