US backing for Syria peace talks hosted by the Russian government in Moscow this week is being seen as further evidence that the Obama administration has quietly dropped its longstanding demand that President Bashar al-Assad step down as part of any settlement.

Russia, supported by Iran, has consistently backed the Assad regime since the civil war began in 2011, even after the UN implicated the Syrian leader in war crimes. The US government and the exiled Syrian opposition, supported by Britain, the EU, Turkey and Saudi Arabia, have argued with equal vehemence that peace is inconceivable while Assad remains in power.

As recently as last October, John Kerry, the US secretary of state, said there would never be peace in Syria “while Assad remains the focus of power”. But now Kerry has changed his tune. At a meeting this month with Staffan de Mistura, the UN’s Syria envoy, Kerry omitted any reference to regime change in Damascus, voluntary or involuntary.

“It is time for President Assad, the Assad regime, to put their people first and to think about the consequences of their actions, which are attracting more and more terrorists to Syria, basically because of their efforts to remove Assad,” Kerry said.

Kerry’s emphasis on the terrorist threat is key to understanding the White House shift. Defeating Islamic State fighters who control roughly half of Syria and large swaths of Iraq has become the Obama administration’s top regional priority, ahead of ending the civil war or cutting a nuclear deal with Iran – though the latter aim would be advanced if Washington and Tehran can agree on Syria.

From the Russian perspective, curbing terrorism in Syria and beyond has always been the most important objective, as Sergei Lavrov, Russia’s foreign minister, reiterated in remarks prior to the three-day peace conference, which opens in Moscow on Monday.

Now Russia clearly believes the Americans have come around to its way of thinking. “There is full conviction in the west that a political solution to the crisis in Syria is inevitable,” Lavrov said.

Not long ago, a Russian-sponsored conference involving officially tolerated Syrian opposition groups, the Syrian regime represented by its UN ambassador, Bashar Jafaari, and a handful of individuals from the main exiled opposition alliance, the National Coalition, would have been dismissed in western capitals as a stunt.

But in what appeared to be an admission that both Washington’s Syria policy and the Geneva peace process launched in 2012 have run out of road, Kerry said he hoped the meeting would be “helpful”.

The state department encouraged Syrian opposition members to go to Moscow. “We’ve certainly conveyed we’d support them attending the meetings,” said spokeswoman Jen Psaki.

Lavrov said he hoped the conference, in which Russian officials will pay no direct part, would help de Mistura relaunch the UN-backed Geneva process, which stalled last year. Both the US and Russia are also supportive of de Mistura’s efforts to arrange local ceasefires inside Syria, such as that in Aleppo.

It has become uncomfortably clear to western governments that the Syrian war, which has claimed more than 200,000 lives, is stalemated and that the Assad regime remains defiantly entrenched. Russian and American analysts suggest the two countries increasingly share a common agenda over Syria: defeating terrorism, stepping up humanitarian ceasefires, and reviving the Geneva process.

While Moscow does not guarantee Assad’s personal future, it will continue to support his regime as Syria’s legitimate government in any Geneva talks. For its part, the US continues to hope Assad will be removed, but is no longer publicly insisting on it as a precondition for a peace deal.

“What’s curious about these Russian priorities is the extent to which they dovetail with White House talking points,” said analyst Tony Badran. “A year-end statement posted on the Facebook page of the US embassy in Damascus defined the US role as leading efforts ‘to meet humanitarian needs, defeat Isil [Isis], and foster a peaceful resolution to the conflict’. Nothing in there about removing Assad,” he wrote.

“Moscow has noted a completely new emphasis in Kerry’s remarks on President Bashar al-Assad and his regime, suggesting that the hitherto irreconcilable US approach has mellowed... It means that Moscow’s and Washington’s positions are no longer as antagonistic,” said Vitaly Naumkin of the Russian Academy of Sciences.

Syria’s main opposition and their Turkish and Saudi backers will not like it, but a big power consensus is building that may enable Assad to survive.

“There seems no chance that Mr Assad will leave power voluntarily any time soon or that he will be forced out by the non-Isis rebels unless the US intervenes directly, a course President Obama has rejected,” a New York Times weekend editorial commented.

“Besides, the greater threat now is not Mr Assad but the Islamic State, especially if it continues to expand in Syria, entices more foreign fighters into its ranks and uses its territory to launch attacks on the west … The unsettling truth is that the brutal dictator is still clinging to power and the United States and its allies are going to have to live with him, at least for now.”