A government encirclement of the Syrian rebel stronghold of Aleppo could be “imminent,” according to military and humanitarian observers, some of whom point to United Nations-sponsored peace talks as having given the regime of Syrian President Bashar Al-Assad maneuvering room.

If Syria’s largest city is surrounded by government troops, the strategic situation in Syria could change very rapidly for the worse, not only for Syrians, but also for Turkish President Recep Tayyip Erdogan—and for the Obama Administration, which has banked heavily on the crumbling peace talks to end five years of civil war and an expanding presence for ISIS amid the chaos.

The encirclement would also be a major strategic advance for Russian President Vladimir Putin, who has drawn down his forces in Syria, but has also been helping the Assad regime conduct more focused military operations under a two-month “cessation of hostilities.”.

“A number of signs, including a higher concentration of air strikes, the movement of Russian artillery support for regime forces, and a variety of skirmishes near a 3-to-4 kilometer gap that still keeps Aleppo from being besieged, all show that they are getting ready to move,” says Chris Kozak, a Syria analyst with the Washington-based Institute for the Study of War.

Recent air attacks on civilian institutions in Aleppo, including the Wednesday bombing of an underground hospital, and attacks on civilians  in other centers are also symptoms of the impending military move, says Valerie Szybala, executive director of the Syria Institute, a Washington-based non-profit research organization.

“The assault on Aleppo that everyone has been expecting is beginning,” she told Fox News. “It doesn’t look good.”

“We think they will move to besiege Aleppo City as soon as they can,” Dr. Khaled Almilaji, a doctor providing emergency medical training for relief workers in the Turkish city of Gazientep, not far from the Syrian border. “We are stockpiling medical supplies in Aleppo City as much as we can.”

The pessimistic analysis of the situation on the ground contrasts sharply with the message of strained optimism that emerged yesterday from U.N. Special Envoy for Syria Staffan de Mistura, who briefed the U.N. Security Council on his efforts to keep the faltering peace talks on life support.

Those talks, he related to journalists after his briefing “have instead been overshadowed, let’s be frank, by a substantial and indeed worrisome deterioration of the cessation of hostilities,” in the past several weeks, following a decision by Syrian opposition forces to withdraw from the talks on April 19.

That withdraw in turn was sparked by opposition charges that the Assad regime and its supporters were already using the “cessation of hostilities” to carry on their military actions. 

The cessation is “still alive, but barely,”  de Mistura insisted, while adding that “the perception is that it could collapse at any time”—a distinction not felt by those affected by recent bombings.

The U.N. envoy declared that even while the Geneva-based peace talks were frozen, progress had been made in a series of “substantial technical meetings”  and consultations among the warring  sides,  interested nations and other Syrian civil groups that had taken place elsewhere.

The “commonalities” from those meetings, according to a “mediator’s summary” made public by da Mistura, included the need for a new Syrian constitution, and a “Syrian-owned and Syrian-led” political transition in the future, overseen by a “new, credible and inclusive transitional governance”  that “could include members of the present government and the opposition, independents and others.”

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Da Mistura hailed the “commonalities” as “an opportunity of going deeper” in future rounds of peace talks, and declared that “we have at least one or two more rounds before July,” when a timetable passed by the Security Council called for the peace process to turn the “commonalities” into actual facts.

Meantime, however, regime aircraft are bombing “on a daily basis,” according to a media spokesman for the volunteer Civil Defense units known as White Helmets, who lost five of their own members during attacks this week,. The attacks are occurring not only in Aleppo but in other major Syrian opposition centers such as Idlib, where rebels have charged that  barrel bombs were used.

Many aid workers, as well as opposition forces, have charged that Russian aircraft were used in the Aleppo hospital strike—charges that have not been confirmed—because regime aircraft are not deemed capable of accurate night-time attacks.

A least 14 people, including two doctors, died in the hospital bombing.  Nearby buildings were also struck, bringing the death toll, including children, to 25 and rising. The “outrageous targeting of yet another medical facility in Syria” was roundly condemned by, among others, Muskilda Zancada, the head of Syrian operations of Medicins Sans Frontieres/Doctors Without Borders,  which supported the hospital.

Overall, according to da Mistura’s Wednesday briefing, “In the last 48 hours, we have had an average of one Syrian killed every 25 minutes.”

A tightening of border controls with neighboring Turkey means that refugees from the violence are less and less able to flee the country even as humanitarian supplies that cross the Turkish border face greater difficulties in reaching the besieged populations.

At the same time, the crisis in long-besieged opposition centers such as the town of Daraya is continuing  to be “absolutely dire,” according to Ashley Proud, humanitarian director for Syria for Mercy Corps, the biggest non-government relief organization involved in cross-border relief operations.

“It is very important for us to support the U.N. but we also need genuine, sustained humanitarian aid for Syrian populations. Humanitarian discussions so far only include discreet convoys for U.N. relief.”

And despite the lengthy “cessation of hostilities,” she added, “most of the places where we work are still really tightly under siege.”

All of those situations would grow dramatically worse in the event of Aleppo’s encirclement, according to the Institute for the Study of War’s Kozak.

“It would be a tremendous morale blow to the opposition,” he told Fox News, “and a tremendous opposition blow to opposition power.”

One result could be to cause links between opposition factions to break down, and drive some in the direction of extremist groups like ISIS, and cause a “deeper radicalization of the opposition in northern Syria.”

The longer term danger is that the military shift would be a “direct blow to the strategic perspective of Turkey’s Erdogan, who has heavily backed the insurgents, “and if Erdogan decides to take a position of support, it would invite retaliation by Russia.”

Indeed, Kozak added, “I think Russia would be ecstatic if Erdogan takes military action.” Moscow is already embedding military support with  Kurdish groups on the Turkish border who would put additional pressure on that country, a NATO member, and thus “provide a new front to pressure NATO.”

Kozak also declared himself “pessimistic” that Western backers of the anti-ISIS campaign and a brokered peace arrangement in Syria would react effectively to any strategic shift caused by Aleppo’s encirclement.

“They are going to be strategically surprised by the most obvious strategic surprise,” he declared. “It may already be too late.”

If so, added the Syria Institute’s Szybala, she believes a major factor in the darkening perspective has been the much touted “cessation of hostilities,” which has “worked to the Syrian government’s benefit.”

“The regime’s big conundrum was that it was unable to carry out offensives on multiple fronts,” she said. “The ceasefire allowed them to focus militarily on a few key areas. Their continued military actions have been tolerated by the international community because no-one wants to see the ceasefire dead.”