Beirut: Syria's main opposition group said it has yet to commit to a US-Russian plan to stop fighting in Syria on Saturday, underlining rebel doubts over a deal they fear will not prevent Russian air strikes against them.
Combatants are required to say whether they will agree to the "cessation of hostilities" by noon on Friday (1000 GMT), and to halt fighting at midnight Saturday. The deal does not include IS or the Nusra Front, an Al Qaeda affiliate which is widely deployed in opposition-held areas.
The United Nations hopes the planned cessation of hostilities will provide a breathing space for Syrian peace talks to resume.
The last round in Geneva broke up earlier this month without progress after the Syrian government launched a Russian-backed offensive on the city of Aleppo, where more fighting was reported on Wednesday.
The HNC, which groups political and armed opponents of President Bashar Al Assad, said on Monday it had "given its acceptance of international efforts for a cessation of hostilities".
But HNC chief negotiator Mohamad Alloush said on Wednesday that the council had not yet decided whether to commit to the deal.
"There was no consultation of Syrians. Will all the observations, additions and amendments requested by Syrians be taken into consideration?," Alloush said in an interview with the pro-opposition Orient TV station.
The opposition fears government forces backed by the Russian air force will continue to attack rebels under the pretext of targeting the Nusra Front.
"How can (Russia) offer guarantees while it is part of the problem," said Alloush, who heads the political office of the Jaish Al Islam rebel group.
The Syrian government, its war effort buoyed since September by the Russian air force, has accepted the cessation of hostilities agreement announced on Monday.
Assad told Russian President Vladimir Putin on Wednesday that his government was ready to assist in implementing the deal, the Kremlin and the Syrian presidency said.
Putin and Assad, who held a telephone conversation, stressed the importance of a continued "uncompromising" fight against IS, the Nusra Front and other militant groups.
Putin has embarked upon a frantic round of telephone diplomacy. The Kremlin described the calls as an effort to explain the substance of the US-Russia-brokered ceasefire.
The Russian Defence Ministry said it had significantly reduced the intensity of its air strikes in Syria in the past two days in areas where armed groups had expressed their readiness to take part in the ceasefire.
Russian state media have presented the fact that Moscow helped broker the potential ceasefire as a sign that Russia matters again on the world stage and has successfully shrugged off what it has cast as US-led efforts to isolate it over the Ukraine crisis.
Turkish President Tayyip Erdogan said he feared the ceasefire plan would do little more than benefit Assad.
Turkey has grown increasingly frustrated by the international response to Syria's five-year-old war, incensed by a Russian intervention which has tipped the balance of power in favour of Assad and by US support for a Kurdish militia it sees as a hostile insurgent force.
"If this is a ceasefire that is up to the mercy of Russia, which has brutally attacked the moderate opposition and aligned with Assad under the pretext of fighting IS, we fear that the fire pouring over innocent people will never stop," Erdogan said in a televised speech.
Relations with Moscow hit a nadir after Turkey shot down a Russian jet near the Syrian border last November, while Ankara's ties with Washington are at their most strained for years.
The Syrian army and IS fought fierce battles on Wednesday near Aleppo, where an attack by the militant group has cut the main land route to the city.
A government military source denied reports the town of Khanaser had fallen to IS, although its fighters were firing on it from nearby positions.
IS is escalating its assaults on government-held areas. Its suicide bombers launched some of their deadliest attacks of the war on Sunday in Damascus and Homs, killing about 200 people. It also attacked government forces near Palmyra on Wednesday.
The attacks appear to be a preemptive move, the military source said, because the militants expect to come under more pressure from the Syrian army soon.
The United Nations carried out its first airdrop of humanitarian aid to the Syrian city of Deir Al Zor on Wednesday, said UN aid chief Stephen O'Brien, delivering 21 tonnes of relief to civilians besieged by IS militants.
"Earlier this morning a WFP (World Food Programme) plane dropped the first cargo of 21 tonnes of items into Deir Al Zor," O'Brien told the UN Security Council.
"We have received initial reports... that pellets have landed in the target area."