But analysts in the region, across the political spectrum, strongly caution that no breakthroughs can be expected soon. Fundamental disconnects remain, and in the diplomatic dance, each side claims that its adversaries are coming around to its point of view.

Russian and Iranian officials suggest that Saudi Arabia, the United States and allies like Turkey are coming to realize that fighting terrorism is more important than ousting Mr. Assad, though Mr. Jubeir insisted after his meeting with Mr. Lavrov that “there is no place for Assad in the future of Syria.” Conversely, American and Turkish officials, who contend that his rule drives radicalism, say that Russia has grown more willing to see him replaced.

And even if real consensus can be reached, any agreement would have little meaning right now, when many forces on the ground still believe they can gain by fighting. Any deal that emerges would be likely to cover only the government-held western spine of Syria and parts of the south, where relatively moderate insurgents are strongest. It is virtually inconceivable that the Islamic State, entrenched in eastern Syria, or the Nusra Front, Al Qaeda’s arm in Syria and a powerful force in the northwest, would be included.

What is nonetheless taking place internationally is a shift in tone, a sense of movement below the surface. That alone is notable in a context of divides that can seem unbridgeable, after four and a half years of fighting that has killed at least a quarter-million people and driven the worst refugee crisis in a generation.

Of all the recent diplomatic exchanges and openings, none is more important than the apparent new spirit of cooperation between Russia and the United States. Fyodor Lukyanov, chairman of a council that advises the Kremlin on foreign policy, said that conversations were returning to the topic of Syria after a year of exclusive focus on the Iran deal, with each side a bit “less firm” in its position.

“Saudi still believes that Assad should go, but now they are a little less sure that the alternative will be better,” he said in a recent interview with The New York Times. “Russia still believes he should stay, but cannot ignore that the general situation is changing, that the strategic position for Syria is much worse now than before.”

Senior American officials say Russian officials have appeared to be more open in recent weeks to discussions about replacing Mr. Assad. These officials, who spoke on condition of anonymity to discuss diplomatic deliberations, say Moscow is increasingly worried about Mr. Assad’s precarious position and the rise of extremist groups, which have recruited several thousand Russian citizens to fight in Syria.