Syria's civil war is in danger of flaring into a regional or even global conflict, but some diplomats hope the high stakes could, paradoxically, pave the way for a peace accord.
Last week, five Russians were likely killed in a US-led coalition bombing on pro-regime Syrian fighters, the Russian government said.
A few days later Israel lost an F-16 warplane in reprisal attacks against Syrian and Iranian military targets after intercepting an alleged Iranian drone.
These serious and unprecedented events were discussed in an urgent mid-week UN Security Council meeting.
"The ingredients for a regional or potentially major global confrontation have come together now, and the risk must be taken seriously," France's UN ambassador Francois Delattre told AFP.
Since the destruction of the Iranian drone "there has been no escalation," said a colleague of Delattre's on the UN Security Council, speaking on condition of anonymity.
But there is now a risk of direct confrontation between the United States and Russia, possibly with new deaths, another diplomat countered.
- Russia cooling on Syria? -
On Wednesday, a Security Council meeting on Syria that was initially slated to be public but was ultimately held behind closed doors, suggested a turning point had been reached.
The language that emerged was a mix of tension and caution that converged on one point: the need for unity to calm things down.
UN ambassador Nikki Haley said peace "is urgent" in Syria, then blamed Iran for its role in the violence.
"On every front of this conflict, we find fighters imported by Iran from Lebanon, Iraq, and Afghanistan," she said.
Haley described it as "a dangerous game of pushing boundaries, instead of behaving responsibly and committing to peace."
Russian ambassador Vassily Nebenzia told reporters that his country is "doing everything to prevent any major international confrontation in Syria. We are working on that hard."
According to Nebenzia, no country has "delivered more than us on the political process in Syria."
He cited Moscow's ties with the Damascus regime and the opposition, its support for so-called "de-escalation zones," and peace talks in Astana and Sochi which Russia says are aimed at facilitating other talks in Geneva.
A diplomat, speaking on condition of anonymity, said that Russia is losing ground even after all it has invested militarily in Syria.
Moscow's influence over Damascus remains tentative, as seen in a recent warning from the Syrian regime on the results of talks in Sochi aimed at forming a committee to amend the Syrian constitution.
Syria does not want its make-up to be dictated by the United Nations, nor does Moscow seem keen on seeing Iran making inroads in Syria and risk regular clashes with Israel.
- 'Dark hours' -
In closed door meetings, Russia, which may be at the end of its military and financial commitment in Syria, speaks of its will to get out of the conflict, insists it has no hidden agenda, and even goes so far as seeking Western help to persuade Damascus, according to this diplomat.
This is a new position after the series of Russian vetoes in late 2017 of Western resolutions that went against Syria.
"The road to peace will come when all of the parties stop provoking each other, and choose the responsible path," Haley said.
In that sense the risk of a major international clash in Syria might open the doors for a breakthrough.
This can serve as "leverage to obtain a peace accord in Syria at a time when lines are beginning to move," said Delattre.
After seven years of a complex and devastating war that has brought in many regional and international actors, "we are back to the darkest hours," diplomats say.
They point out a list of besieged areas such as eastern Ghouta, Idlib and Afrin, the target of a Turkish military operation against Kurdish militia forces allied with the United States.
The operation has created tension between the United States and Turkey, two key members of NATO, a military alliance dominated by Washington.
Due to this tension, NATO strategic interests are now affected by how the balance of power in the Syrian war evolves.