Secretary of State John Kerry has met with his Russian counterpart, Sergey Lavrov, to discuss a resolution to the Syrian crisis. The US has not participated in the latest round of peace talks in Ankara, however. Thomson Reuters The US was shut out of a new round of negotiations between Russia and Syrian rebel factions hosted by Turkish officials in Ankara, a source within the Syrian opposition told Business Insider on Monday.

The opposition source, who spoke on condition of anonymity because he was not authorized to discuss the negotiations, said American officials were not invited to take part in the talks because of recent tensions between Turkey and the US.

"The US is totally out of these talks," this person said. "And they're pretty angry about it."

The State Department would neither confirm nor deny that the US had been shut out of the talks. But an official pushed back against the notion that the Obama administration was vexed by the Turkey-brokered negotiations.

"We have seen reports of talks taking place between Russians and Syrian rebels, and we would welcome any genuine efforts to ease the suffering of the Syrian people, particularly in Aleppo, which has endured so much hardship in recent months," a State Department official told Business Insider on Tuesday.

The official also said that US representatives are "deeply engaged" with various partners on Syria.

"The US remains deeply engaged with the Turks, Russians, Saudis, and Qataris, our European allies, and the opposition in Syria," the official said. "Secretary Kerry met with [Russian] Foreign Minister [Sergey] Lavrov and Special Envoy [Staffan] de Mistura in Rome Friday, and has meetings with multilateral partners in Europe this week."

The State Department announced in October that the US was severing its bilateral channels with Russia over Syria amid Russia's "intensified attacks against civilian areas," aid workers, and hospitals in Aleppo. Kerry has continued to meet and speak regularly with Lavrov about Syria since then, however.

Russian Foreign Minister Sergey Lavrov, left, and US Secretary of State John Kerry, right, attend a meeting in Rome on December 2. Gregorio Borgia/Pool/Reuters

Mikhail Bogdanov, Russia's deputy foreign minister, did not say last week whether Russian officials were negotiating with Syrian opposition factions in Ankara.

"We need no mediators with the Syrian opposition. We have direct contacts," he told the Russian news agency TASS.

Among those present at the Ankara talks, according to the opposition source, were representatives from the Islamist rebel coalition Ahrar al-Sham. The Islamist al-Zenki rebel faction, which received US-made anti-tank missiles between 2014 and 2015, was also present — at Russia's invitation, according to The Telegraph.

The talks have been aimed at securing a deal to deliver humanitarian aid to eastern Aleppo — the Syrian city that has been besieged and under relentless aerial bombardment for more than three weeks — in exchange for the evacuation of extremists groups like the former Al Qaeda affiliate Jabhat Fateh al-Sham.

"Russia has indicated it'd be willing to accept aid access and local council control of Aleppo's east in exchange for JFS's withdrawal," Charles Lister, a Syria researcher with close ties the opposition, tweeted on Saturday.

Separate negotiations between Russia and the US were apparently underway last week to evacuate rebel groups from Aleppo, allowing civilians to stay and receive humanitarian aid. But on Tuesday, Lavrov said from Moscow that "those who refuse to leave of their own accord will be wiped out."

"There is no other solution," he said.

The US has also been negotiating with rebel groups inside Aleppo to try to negotiate the terms of their departure from the city, according to The Washington Post.

But the Free Syrian Army, a prominent coalition of rebel groups opposed to Syrian President Bashar Assad, is not considering withdrawing from eastern Aleppo, said Asaad Hanna, a political officer in the FSA.

"We will keep fighting," Hanna told Business Insider on Tuesday. "There are no preparations being made for the FSA to evacuate, and civilians haven't asked us to either. They feel they need protection from the [Iran-backed] militias and Hezbollah."

Forces backing Assad, including Iranian-led Shia militias and Lebanese Hezbollah fighters, took back roughly 40% of the rebels' territory in eastern Aleppo last week amid heavy airstrikes from Russian and Syrian warplanes.

Turkey, echoing a proposal put forward by the UN last week, has been urging Russia to stop the bombing long enough for the 100 to 400 JFS fighters in eastern Aleppo to exit the city so that they would no longer be embedded with more moderate rebel groups and civilians.

Amid thawing relations with Turkey, Russia — which believes there are thousands, and not hundreds, of JFS fighters in the city — was considering the request.

As of Tuesday, however, a deal had still not been finalized. The talks are expected to continue throughout the week.

People who came back to inspect their homes walk near government soldiers in Aleppo. Reuters/Omar Sanadiki

Further complicating the negotiations is the feeling that Russia, which changed the tide of the war when it intervened on behalf of Assad in October 2015, may be losing influence in Aleppo.

"The Russians would prefer to have a cease-fire to help their relations with Turkey and show they are interested in peace, but the regime and the Iranians, they don't care," Bassam Barabandi, a former Syrian diplomat who is now a political adviser to the opposition High Negotiations Committee, told The Guardian last week.

"They want to take all of Aleppo," Barabandi said. "For the Russians, failing to achieve a cease-fire in Aleppo will show just how weak they are."