LONDON - The latest US and Russian bid to find enough common ground on which to build some hope for Syria is in trouble, just days ahead of talks that could make or break the peace process.
A United Nations mediator has called on Bashar al-Assad's regime and a beleaguered opposition coalition to send envoys to Geneva on November 28 to resolve the seven-year-old civil war.
This comes less than a week after Presidents Donald Trump and Vladimir Putin issued a joint statement agreeing that there is "no military solution" to the conflict.
US officials then welcomed the statement as a sign of Russia's commitment to a UN-backed political process that Washington feels must lead to an end to Assad's bloody rein.
But if their show of optimism raised cynical eyebrows then, it seemed even less plausible by Friday, after the latest heated showdown over Syria at the United Nations.
There, Russia moved to thwart international attempts to salvage a UN-led probe into Assad's and extremist groups' use of chemical weapons to slaughter Syrian civilians.
Washington's ambassador to the United Nations, Nikki Haley, was clear about what the Russian veto of a US-backed resolution meant for the broader peace process.
- Fruitless forays -
"Russia proves they cannot be trusted or credible as we work towards a political solution in Syria," she declared.
The previous US administration under Barack Obama repeatedly tried and failed to engage Putin with a peace plan that would lead to a political transition away from Assad's rule.
Then secretary of state John Kerry's frequent but fruitless forays to hotel conference rooms in Vienna and Geneva to spar with Foreign Minister Sergei Lavrov were much mocked at home.
But, despite the undeniable progress that a US-led military coalition has made against the Islamic State group's Syrian strongholds, Putin has remained loyal to Assad.
And US diplomats now hope not only to nudge Russia into bringing him to the table, but also to have Moscow help them oust Syria's other main ally, Iran, from the battlefield.
If Russia, in Haley's words, is "no longer trusted or credible" -- what hope can there be of this plan, with UN envoy Staffan de Mistura's November 28 peace talks fast approaching?
State Department spokeswoman Heather Nauert shared Haley's disgust with Russia's opposition to the UN chemical weapons probe, saying: "We were very disappointed."
"We know that Russia one again prioritized protecting the Assad regime," she said, while insisting this was no death knell for the broader peace process.
"There are a lot of areas where we don't see eye-to-eye with Russia, but there are some areas where we do see eye-to-eye."
- Ceasefire zone -
Nauert noted that Moscow and Washington agree on the need to destroy IS, and have worked together to set up a ceasefire zone in southwest Syria.
"So the secretary and the president and Mr Lavrov and Vladimir Putin have agreed to try to put together another one," she said.
"If we can do that, and we can find this area of agreement, it could potentially bring in more aid and save lives and try to get Syria more stable."
But, asked if Russia could be a US partner in saving the Geneva process toward a settlement, she admitted: "I don't know."
Many observers scoff at that idea, and most doubt that Putin, having risked Russian troops and planes to save Assad, would now encourage a peace process that would see him step down.
And western diplomats say that, in private, some senior US officials admit that Assad and Putin effectively won the war two years ago and are now just consolidating victory.
To give that a veneer of international respectability, Moscow has set up its own peace process in Astana with Turkey and Iran as co-guarantors -- leaving aside the US and UN efforts.
"The Russians are doing everything they can to drain Geneva of its substance and replace it with a process they control," said Joseph Bahout, Middle East scholar at the Carnegie Endowment for International Peace.
For Bahout, the Trump-Putin joint statement was meant to paper over the cracks in the breakdown, but the bitter row at the United Nations paints a clearer picture of relations.
Even the ceasefire zone, and its application, has been a source of tension. The United States saw it as a sign that Russia is amenable to countering the Iranian role.
The southwestern area covered by the agreement is largely held by Iranian-backed forces, such as Lebanon's Hezbollah, and Washington hoped the deal would lessen Israeli concerns.
But when US officials talked this up as a success, Lavrov responded sharply that the ceasefire deal had nothing to do with concern about Iranian forces.
"Since then, the climate has worsened," he told AFP. "What's happening at the UN is in part a result of those tensions."