In Syria's largest city, the streets are quieter than normal: Tens of thousands of people have fled Aleppo and its northern suburbs over the last week since an increase in Russian airstrikes in support of embattled President Bashar Assad. Those who stayed behind are reporting on social media that the bombings are intensifying with each passing day, coming in rounds of three, stopping for four hours and returning with a vengeance at night. Although the U.S. has denounced Russia’s killing of innocent civilians, its efforts to convince Russia to back off are failing, analysts say, because of the Obama administration's negligible political leverage.

“It is hard to have leverage in a war when you are reticent to use military force,” said Andrew Tabler, an expert on Syria at the Washington Institute for Near East Policy. “This White House doesn’t want to use military force in Syria. It has been clear about that from the beginning. It’s hard to think about things going any differently.”

RTX1GSXQ Men search for survivors at a site hit by what activists said was heavy shelling by forces loyal to Syria's President Bashar Assad in the Douma neighborhood of Damascus, June 16, 2015. Photo: REUTERS/Bassam Khabieh

The bombardment of Aleppo — and the subsequent exodus of terrified residents — came just one week after United Nations-brokered peace talks in Geneva fell apart. The talks were supposed to bring together political factions in Syria to discuss a solution to end the five-year conflict but broke down after opposition parties walked out.

Rebel groups are losing on the battlefield as well as in the conference room. Russian airstrikes this month led to a massive retreat by U.S.-armed opposition forces, allowing Assad’s troops to advance and capture strategic roads that lead directly into the center of downtown Aleppo. Now that the opposition is retreating from the north’s major stronghold, the U.S. is at a disadvantage in negotiations, said Paul Salem, vice president for policy and research at the Middle East Institute, a think tank in Washington.

Syria-talks-Geneva U.N. envoy Staffan de Mistura shakes hands with Syria's U.N. ambassador, Bashar al Jaafari (left) during the Syria peace talks in Geneva on Jan. 29, 2016. Photo: REUTERS/Jean-Marc Ferre/United Nations “Russia has entered decisively into Syria. It is backing one side completely. Clearly, it chose the military offensive as its main instrument,” he said. “The U.S. has no leverage at this point in the conflict. It said Assad must go but has not given any support to the opposition that would make that happen ... Russia has outplayed the U.S.” 

For months, the U.S., led by Secretary of State John Kerry, has tried to bring involved parties to the negotiating table to agree on a framework that would de-escalate the violence and end the civil war through diplomatic means. So far, though, the conflict, especially in the northern part of the country, has only grown more entrenched. The only public response the U.S. has given is via State Department and Pentagon officials in press briefings. In Monday’s presser, State Department spokesperson John Kirby said: “We continue to monitor the situation in Aleppo closely,” adding that Kerry had spoken to Russian Foreign Minister Sergey Lavrov about the bombings and conveyed to his counterpart that the U.S. condemned the killing of innocent civilians.

According to civilians living in Aleppo, Russian bombings have targeted moderate rebels supported by the U.S. and it's anti-Islamic State coalition allies, killed civilians and displaced thousands of people.

“The situation in Syria is teetering on the edge of collapse,” said Perry Cammack , an associate at Carnegie Endowment’s Middle East Program.

One young boy, in a video posted on YouTube that shows Syrians fleeing to the border of Turkey, describes why he and his family fled their home.

"The reason [we are fleeing] is because of the bombings of Russia and Iran and Bashar ... because of the Shiite armies. That is why we are leaving," he said. Several other people interviewed in the video said Russian bombs were the cause of the mass flight to the border.

The regime’s advances and the opposition’s military failures are a product of the Obama administration’s policy of staying out of the frays of the war, keeping U.S. soldiers, besides a select group of special ops, home in America, Syria analyst Tabler said.

“They [the Obama administration] don't want to escalate, they want to de-escalate,” Tabler said.

It is in pursuit of this goal that Kerry was set to meet Lavrov in Munich Thursday, with an emphasis on delivering humanitarian aid to besieged areas and renewing suspended peace talks in Geneva, according to a statement released by the Russian Foreign Ministry. 

But, while talks are pending, at the Bab al Salama border crossing north of Aleppo, thousands of mothers, fathers and children stand waiting for the Turkish officials to open the gates to release them from the Assad regime and Russian bombardments. Until now, Turkish authorities have prevented the Syrians from passing into Turkey. More than 10,000 people are now stranded in a makeshift internally displaced persons camp without access to vital medical services.

The humanitarian crisis on the border will not change until the U.S. can convince Russia and its allies to agree to establishing a safe zone that would allow aid to cross the border but many analysts remain unconvinced that Kerry has the diplomatic power to push it through.

As the Middle East Institute's Salem told International Business Times: “Kerry has very little to work with. Diplomacy doesn't work unless you have serious leverage and you can squeeze things out of the other party.” 

At the moment, it seems the only side who is prepared to do any squeezing is Russia.