Russian-backed peace talks aimed at ending the Syrian war brought rebels and the Syrian government face to face for the first time Monday, marking the launch of a new role for Russian President Vladimir Putin as a Middle East power broker.

There was no indication that any progress was made on the first day of what is expected to be a two-day event, taking place in a conference room in the Turkish-owned Rixos Hotel in Astana, the capital of the central Asian nation of Kazakhstan.

There is cautious optimism, however, that the talks may go further than previous failed efforts because of the evolving role of Russia, a critical political and military backer of Syrian President Bashar al-Assad.

In the past, Moscow frequently acted as a spoiler when the United States was driving the diplomacy on Syria, but it is now embracing a role as mediator between Assad’s government and moderate rebels once denounced by Russian officials as terrorists.

Turkey and Iran are co-sponsors of the talks, but it is Moscow that has thrown its prestige behind the effort to bring the warring factions together, leaving little doubt that this is a Russian-led process, diplomats said. The United States, meanwhile, has been relegated to observer status and has not been a party to the intensive negotiations preceding the talks.

Even the choice of location spoke to the emerging Russian role. Astana, a remote and snowbound city in Kazakhstan, a former Soviet republic, lies close to the Russian border and nearly 6,000 miles from Washington.

“We’re in uncharted territory,” said Noah Bonsey, a senior analyst for the International Crisis Group, who was in Astana. “We’re here in Russia’s back yard, and the ball is in their court. There’s a new political and military dynamic, and it is happening on Russian political turf.”

In an early success for Moscow’s diplomacy, representatives of Assad and the Syrian rebels seeking to overthrow him sat together in the same room for the opening session of the talks — the first time they have encountered one another directly since the bloodshed began in 2011.

Participants said the mood was frosty as the warring factions took their places on opposite sides of the conference room. Between them were representatives of Russia, Turkey and Iran, and the United Nations’ top Syria envoy, Staffan de Mistura. The U.S. ambassador to Kazakhstan, George Krol, attended as an observer.

Hopes for a breakthrough immediately faded. The head of the Syrian government delegation, Syrian U.N. Ambassador Bashar Jaafari, denounced the opposition as “terrorists” in his opening remarks. The opposition said it did not believe that the government was serious about seeking a settlement.

There were no immediate plans for direct negotiations between the two sides, apart from their encounter at the opening session. For subsequent meetings, the rival delegations met in separate rooms, with the U.N. envoy shuttling between them.

The sponsors have set the relatively modest goal of strengthening a shaky cease-fire that was introduced late last month but has been widely ignored in many locations. The Syrian opposition delegation is composed entirely of representatives from rebel groups, and the Syrian government delegation includes officers with the Syrian army.

That the rebels and the government were even in the same room nonetheless was a small step forward. The Syrian government has in the past met face to face with members of the political opposition at peace talks in Geneva, but it has refused to meet with the armed opposition, which it has consistently labeled as “terrorists.”

The biggest shift, however, has been in the position of the Russians, who until recently shared the Syrian government’s view that there are no “moderate” Syrian rebels. That changed in December, after the military defeat of the rebels in their symbolically vital stronghold of east Aleppo. The rebels’ collapse was also a defeat for U.S. diplomacy, which had been focused on securing a cease-fire in Aleppo.

Russia has since moved forcefully to the center of the international diplomacy, sidelining the United States and its European and Persian Gulf Arab allies while reaching out to Turkey and Iran, the two nations with the most influence on the ground in Syria.

Turkey controls the border on which the rebels rely for their supplies and has troops fighting alongside rebels against the Islamic State in a pocket of territory in northern Syria. Iran sponsors and funds many of the militias fighting on the ground on behalf of Assad, including the powerful Lebanese Hezbollah militia.

Moscow has also courted the rebel groups it previously rejected as potential negotiating partners when Washington was trying to promote talks. The opposition delegation was headed by Mohammed Alloush, a political officer with the Islamist Jaish al-Islam group, which Moscow previously sought to persuade the United States to designate as a terrorist organization.

“It’s a big shift. Russia has realized that those people they were calling terrorists, they can talk to them,” said Yahya al-Aridi, a spokesman for the rebel delegation. And after their military defeats, the rebels realize they have no choice but to negotiate with Russia, he said.

“We are not falling in love with the Russians. We do not forget they targeted markets and hospitals with their planes,” he said. “But this change is something to welcome, and we are ready to help it, especially if it results in a situation where Syrian children are not being killed on a daily basis.”

In one sign that Russia appears to be serious about pressuring the Assad regime to make concessions, the Russian military issued a statement explicitly accusing the government of violating the cease-fire.

Russian officials say they do not intend for this initiative to supplant the U.N.-backed Geneva peace process, which has sputtered on for the past four years without success but remains the only internationally recognized formula for ending the war.

A new round of Geneva talks is due to begin Feb. 8. The hope is that any agreements on a cease-fire reached at Astana will help build confidence for the more challenging task of negotiating a wider political settlement. As a member of the U.N. Security Council — along with Russia — the United States will play a bigger role in those talks, but how remains in question because the new administration of President Trump has not yet articulated a position on Syria.

Trump has, however, suggested that better ties between Moscow and Washington could bring better coordination in the fight against the Islamic State, which is not covered by the cease-fire talks.

In Moscow, Kremlin spokesman Dmitry Peskov told reporters that Putin and Trump could “very soon” have their first phone conversation since Trump took office.

The fate of Assad, which is not on the agenda for the Astana talks, is the thorniest long-term obstacle to peace. The rebels will not accept any solution to the war that does not include the president’s eventual departure, Aridi said. Representatives of the government say Assad’s position is not up for discussion.

Zakaria Zakaria in Istanbul and Brian Murphy in Washington contributed to this report.