An image obtained from the official facebook page of Syrian Presidency shows Syrian President Bashar al-Assad speaking to the press following a meeting in Damascus on November 14, 2015
Beirut (AFP) - Hopes for a quick political transition in war-ravaged Syria dimmed Thursday as embattled President Bashar al-Assad threw cold water on an ambitious timetable agreed at international talks in Vienna.
At the same time, the US held firm to its calls for Assad's departure, with President Barack Obama insisting the war could not end unless the Syrian leader steps down.
"I do not foresee a situation in which we can end the civil war in Syria while Assad remains in power," said Obama.
Top diplomats from 17 countries met in Vienna Saturday to discuss a way out of Syria's nearly five-year conflict, which has killed more than 250,000.
They produced a two-year timetable: a transitional government would be formed and a new constitution written within six months, to be followed by internationally monitored elections within 18 months after that.
But in a television interview with Italy's Rai television, Assad said there could be no transition schedule for elections while swathes of Syria remained out of government control.
"This timetable starts after starting defeating terrorism. You cannot achieve anything politically while you have the terrorists taking over many areas in Syria," he said.
"If we talk after that, one year and a half to two years is enough for any transition."
Damascus refers to all opponents -- fighters and activists alike -- as terrorists.
- 'More realistic than Vienna' -
Syria's government has insisted that combatting "terrorist groups" including the Islamic State (IS) jihadist organisation should come ahead of any political solution.
Assad also rejected the idea of UN observers monitoring elections, saying the world body had "lost all credibility".
In comments to French magazine Valleures Actuelles, the embattled leader said Syria could only accept observers from countries that "were not partisan during the crisis".
Meanwhile, Russian Foreign Minister Sergei Lavrov said Moscow would be ready to work with the Western coalition striking IS if its members respect Syria's sovereignty.
Russia is "ready to develop with them such forms of coordination that of course would respect Syria's sovereignty and the prerogatives of the Syrian leadership," said Lavrov.
Despite holding diametrically opposed views on the fate of Assad, Russia and France are set to begin coordinating military and security efforts in the anti-IS fight.
The remarks by world leaders have rolled back hopes a political solution was on the horizon.
On Tuesday, US Secretary of State John Kerry said Syria could be "weeks away" from a transition.
But Waddah Abed Rabbo, editor-in-chief of Al-Watan daily close to the government, said: "Syria's president is much more realistic than the Vienna declaration.
"Can we imagine elections in Raqa or Deir Ezzor?" he said, naming two provinces where IS has a strong presence.
"We must first eliminate this scourge and re-establish the presence of the state throughout the whole country, before beginning the countdown to elections."
- Truce talks under pressure -
IS territory across eastern, central, and northern Syria is the target of a US-led air coalition as well as Russian strikes.
Air strikes on fuel trucks in IS's de facto capital, Raqa, killed at least six civilians and wounded 20, said the Syrian Observatory for Human Rights.
Observatory head Rami Abdel Rahman said those killed were oil smugglers and their families, not jihadists.
Another eight people were killed and 20 wounded in government shelling of an olive press in Sheikh Maskin, in the southern province of Daraa, the Observatory said.
Meanwhile, Syria's army and rebels struggled to pursue talks to reach a 15-day ceasefire in the Eastern Ghouta rebel stronghold east of Damascus.
The two sides had been locked in talks overnight in the hopes of reaching a deal by 6:00 am (0400 GMT), in what would be the first temporary truce in Eastern Ghouta.
After hours of relative quiet Thursday morning, Syria's armed forces resumed shelling Douma, killing 12 people and wounding 70, the Observatory said.
"The mediators are still at work," but the situation was less hopeful than this morning, Abdel Rahman said.
A Syrian security source said "the window to reach an agreement has not ended, but we have yet to reach the results stage."
The Observatory said rebel shelling of the capital wounded 16 people.