The United Nations is warning of catastrophic consequences facing civilians trapped in Syria's Idlib province.
"The conflict in Syria has already caused unspeakable suffering to millions of people forced to live under siege or to leave their country," warned Olaf Skoog, the permanent representative of Sweden to the United Nations. "We are deeply concerned about the escalating military action by the Syrian regime and Russia in northwest Syria with potentially catastrophic humanitarian consequences for civilians."
Residents of Syria's Idlib province took to the streets Friday protesting against what many there believe is an impending assault in the region.
"Leave, Bashar!" hundreds of protesters chanted in Saraqeb, a town in eastern Idlib. "We will defend our revolution."
For weeks, Syrian forces, backed by Russian, Iranian and Turkish fighters, have encircled the province which is now the rebels' last stronghold position.
The UN envoy for Syria says there are at least 10,000 Al Qaeda-linked terrorists in Idlib, along with some 70,000 other fighters from various Islamic terror groups controlling roughly 60 percent of the province.
For weeks, Syria's military has been dropping leaflets urging rebel fighters in Idlib to give up their arms and surrender.
Iran's president says the battle will end once all extremists are "uprooted" from Idlib.
"The fight against terrorism in Idlib is an unavoidable part of the mission to bring back peace and stability to Syria," Iranian President Hassan Rouhani told reporters Friday.
A Russian official echoed similar sentiments.
"A total and definitive liquidation of the terrorists across all of Syria's territory is necessary," Russian Foreign Ministry Spokeswoman Maria Zakharova told AFP.
Meanwhile, a spokesman for one of the rebel groups operating inside Idlib told the Associated Press that his fighters are ready for a showdown.
"We've reinforced our defensive points and lines, we've prepared strong fortifications to withstand airstrikes so that we don't lose our fighters," said Naji Moustafa, a spokesman for the National Front for Liberation.
"We will deal with their strength in a tactical manner to absorb their airstrikes and their ground attacks and their scorched earth strategy," Moustafa told the AP. "We've prepared our fighters qualitatively - we've trained them on the military tactics to deal with these scenarios."
Syria, with help from Russia and Iran, has waged a brutal campaign over the past two years to recapture territory once held by the rebels. Idlib is the final stand, and the fall of the city would effectively mean the end of Syria's brutal civil war.
Rouhani, along with the leaders of Turkey and Iran met in Tehran Friday to discuss how to limit civilian causalities.
"Any attack launched or to be launched on Idlib will result in a disaster, a massacre, and a very big humanitarian tragedy," said Turkish president Recep Tayyip Erdogan. "We never want Idlib to turn into a bloodbath."
Turkey's role in Idlib is complicated. For several years, the Turkish regime in Ankara has backed Syrian rebels fighting Assad. Now, Turkey's president is calling for a ceasefire, fearing a major military offensive could prompt millions of additional Syrians to flood the Turkish border.
"We have to take joint steps to prevent the migration," Erdogan said. "Turkey is already sheltering 3.5 million refugees (from Syria). The population of Idlib is 3.5 million. Turkey doesn't have the strength or capability to host 3.5 million more," he added.
Nearly half of Idlib's residents are already displaced from other parts of Syria.
"The dangers are profound that any battle for Idlib could be, would be, a horrific and bloody battle," warned Staffan de Mistura, the UN envoy for Syria. "Civilians are its potential victims and they are ever-present dangers in the case of a full-scale assault of incidents or rapid escalations involving regional and international players."
America's ambassador to the UN is warning Russia, Iran, and Syria that the "consequences will be dire" for an assault on the province.
"The United States has been very clear, with Russia and with the broader international community: we consider an assault on Idlib to be a dangerous escalation of the conflict in Syria," Ambassador Nikki Haley told the UN Security Council on Friday. "If Assad, Russia, and Iran continue, the consequences will be dire."
Iran's president shot back, demanding that the United States withdraw its forces from Syria.
"We have to force the United States to leave," Rouhani said.
The US has 2,000 troops fighting ISIS and other Islamic terror groups inside Syria.