Alarm over the sweeping expansion of the Islamic State (IS) jihadist group in Syria and Iraq means that international priorities have shifted away from Assad's removal.
"Assad has improved his position internationally. The US, EU states and others are no longer demanding his immediate departure," said Volker Perthes, director of the German Institute for International and Security Affairs.
In the four years since the conflict erupted in March 2011, leaving more than 210,000 people dead, Assad's forces have succeeded in halting gains by Western-backed rebels and jihadists seeking his overthrow.
While rights groups still regularly accuse Assad of indiscriminately killing his own people, sending helicopters to drop crude barrel bombs, even the Syrian opposition no longer demands his resignation as a precondition for peace talks.
"Statements from the US and from EU capitals indicate a de facto direct or indirect acceptance of Assad's holding on to the presidency, and a search for some form of national unity coalition that would include Assad as well as the non-jihadist opposition," Perthes said.
- 'Untenable position' -
A European diplomat who often travels to Damascus said EU states are divided on how to deal with the man described by French Prime Minister Manuel Valls just last month as a "butcher".
"Outside of France, Britain and Denmark, who reject any role for Assad in Syria's future, many European countries think that after four years, this position is untenable," the diplomat said.
He said countries including Sweden, Austria, Spain, the Czech Republic and Poland see no benefit to isolating Assad and want a softer European stance.
"But they are too weak to have their voices heard," he said.
US Secretary of State John Kerry recently laid bare the shifting Western stance towards the Syrian leader.
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Assad "has lost any semblance of legitimacy," Kerry said.
"But we have no higher priority than disrupting and defeating Daesh," he added, using an Arabic acronym for IS.
Assad, seen briefly as a reformer at the onset of his rule nearly 15 years ago, was ostracised for his bloody repression of anti-regime protests that began in 2011.
But in remarks that enraged the rebels, UN envoy Staffan de Mistura recently described the president as "part of the solution" in Syria.
"The Syrian regime, and especially its head, is the interlocutor for the international community -- even if officially, the West, Arab states, and Turkey don't talk to him," said Souhail Belhadj, researcher at the Geneva Graduate Institute and author of "Bashar's Syria: Anatomy of an Authoritarian Regime".
- Diplomatic window -
After suffering initial losses to rebels, Assad has managed to stabilise the military balance and even make gains in some areas, thanks to significant support from the Lebanese Shiite militia Hezbollah and the Iranian Revolutionary Guard.
Air strikes by the US-led coalition have piled further pressure on jihadists who have flocked to the war-wracked country.
Today, the regime controls 40 percent of Syrian territory home to 60 percent of the population.
Almost all of Syria's major cities -- except IS's self-proclaimed capital Raqa and half of the second city of Aleppo -- are under government control.
But the battle is far from over.
"The Syrian regime certainly feels it is in an advantageous position with regard to the military situation," said David Lesch, professor of Middle East history at Trinity University in Texas and author of "Syria: The Fall of the House of Assad".
"On the other hand, I think elements within the regime recognise that there may be an economic horizon sooner rather than later in terms of its dwindling manpower, finances and resources, especially when its two strongest allies, Iran and Russia, are suffering economically," he said.
Assad has a "window of opportunity" to negotiate in the coming months before the looming 2016 US presidential election starts to restrict Washington's flexibility on Syria, said Lesch.