The U.N.'s special envoy for Syria, Staffan de Mistura, warned on Wednesday that a full-scale battle in the country's southwest could affect an area and a population similar to those of eastern Ghouta and Aleppo combined, the sites of the two biggest and bloodiest campaigns of the seven-year Syrian civil war.
Briefing the U.N. Security Council, de Mistura said a full-scale battle in the southwest, which is supposed to be covered by a de-escalation cease-fire agreement, would also add to tensions with Israel.
But the Syrian ambassador said it was the army's duty to fight "terrorism" anywhere. He was supported by the Russian ambassador.
International aid organizations sounded the alarm on behalf of thousands of desperate Syrians fleeing the onslaught of President Bashar Assad's forces in southwestern Syria, urging neighboring countries to take them in.
The calls come as Jordan, which already has taken in a registered 660,000 Syrian refugees and is estimated to have many more unregistered refugees, has said it will not open its borders to the Syrians, asking the U.N. to provide them with security within their home country instead.
Israel has not commented on the wave of displacement, although Syrians say many of the displaced have sought refuge near the border with the Israeli Golan Heights.
On Wednesday, Syrian media said government forces, with air cover, were heading toward the Jordanian border.
"We see a full-scale ground offensive and aerial bombardment, as well as exchanges of fire from both sides," de Mistura said, speaking via videolink from Geneva.
He said the battle could affect a population and an area similar to those affected by the battles for eastern Ghouta and Aleppo combined.
The Security Council could not allow another battle of such magnitude, he added.
Syrian Ambassador Bashar al-Ja'afari accused de Mistura of making a dangerous statement by telling the Security Council what it would allow.
"Is this within the mandate of the special envoy, your excellencies?" he asked diplomats in the chamber.
Ja'afari said de Mistura had neglected the fight against terrorism, saying that Islamic State fighters were still in Syria "under the protection of the Americans." The banned Nusra Front group was also still in Syria, protected by "the Americans, the Israelis, and others," he said.
Ja'afari blamed terrorists for attacking residential areas in the south of the country, and said it was the Syrian army's duty to respond to protect hundreds of thousands of civilians.
Russian Ambassador Vasily Nebenzia supported him.
"The cities of Daraa and Sweida, as well as residential areas that have embraced de-escalation, are being subjected to shelling by jihadis," he said.
U.S. Deputy Permanent Representative Jonathan Cohen said the predominant opposition force in the area was the Free Syrian Army, not terrorists and not a permitted target designated by the U.N.
Russia has launched airstrikes in recent days in support of Assad's forces in an offensive that is taking a significant toll on civilians, breaking a year-long calm under the de-escalation agreement in the area, he said.
"To be clear, the unilateral operations underway by the Assad regime and Russia in southwest Syria represent a violation of the cease-fire arrangement reaffirmed by President Trump and President Putin," Cohen said.
Meanwhile, the Russian military said Wednesday it had received a tip about a "provocation" involving the alleged transportation of chemical weapons in northern Syria.
The Russian military's Reconciliation Center in Syria said residents of the northern province of Idlib had called to report that a truck loaded with tanks of unidentified liquid, rockets and protective gear arrived in Idlib over the weekend.
It said the truck was escorted by several vehicles emblazoned with the emblem of White Helmets volunteer first responders. The center said several people clad in protective gear later loaded the rockets with unidentified liquid and powder and took them in the direction of Maarat al-Numaan.
The Syrian government has denied using chemical weapons, and its Russian ally has accused activists of making false claims of chemical attacks.
The U.N. said up to 50,000 Syrians, including 20,000 children and their families, have already been displaced by the fighting in just three days.
"We are receiving reports about people fleeing as the front lines shift," said Robert Mardini, the regional chief for the International Committee of the Red Cross.
"We ask those fighting and neighboring countries to facilitate civilians' access to safety and essential services, including life-saving medical care. Civilians should, as always, have options to flee the violence and seek refuge and protection."
The Norwegian Refugee Council specifically urged Jordan to take in thousands of Syrians, saying they have "nowhere else to turn" as they flee Assad's forces, which began their offensive in southern Daraa province on June 19.
But it said Jordan cannot be expected to shoulder the burden alone, and the international community must "offer substantial support." It added that aid groups are ready to help potential new arrivals settle in Jordan's Azraq camp, which it estimates can house 80,000 more people.
"The situation on the ground in Syria seems to be extremely worrying," Daniel Gorevan of the NRC told The Associated Press. The NRC estimates that 70,000 Syrians have fled the violence and thousands of families are being pushed further south "where they eventually" will run into Jordan's closed border.
"Jordan has done so much over the last years to accommodate so many Syrian refugees and we are calling for the international community to support Jordan to make this division to host these refugees," Gorevan said.
The executive director of UNICEF, the U.N children's agency, said Wednesday that the violence in southern Syria has displaced thousands of children in just three days and has killed several.
"Horror knows no limit in Syria," Henrietta H. Fore said in a statement. "Those wishing to flee should be allowed to reach safe havens, away from the sights and sounds of war. ... The children of Syria have lived through unacceptable suffering. This cannot become the new normal."
The U.N. said the escalation over the last two days suggests there is "little commitment to the de-escalation agreement."
Syrian government shelling since June 17 has destroyed a health center, a civil defense center and put a hospital out of service. In one town, shelling destroyed some 40% of the houses, the U.N. said.
