– Syrian rebels said Tuesday that they are taking part in a new round of surrender talks in the country's southwest after an escalating military campaign displaced more than a quarter of a million people in just two weeks.

Backed by Russia and Iran, the long-heralded offensive has forced terrified families from place to place, trapping them in frontier towns as the violence creeps closer and the borders with Israel and Jordan remain shut.

This slice of southern Syria, the last opposition-controlled territory without a major foreign sponsor, has evolved in recent years into a geopolitical tinderbox. Both neighbors are watching anxiously as the displaced reach their borders and Iran deploys militias alongside the regular forces of Syrian President Bashar al-Assad.

On Tuesday, Ibrahim al-Jabawi, a spokesman for the rebels' negotiating delegation, said the group has returned to talks with Russia, a key backer of Assad's government, in an effort to strike a deal that would apply to the entire opposition-held pocket.

"The talks are going on now," he said, reached by phone. "It could take a day, it could take a week, but we are clear that a solution needs to be reached."

A fragile peace had frozen fighting across the area for almost a year following a cease-fire agreement that President Donald Trump cited as a test of whether the United States and Russia could work together in a conflict that has pitted them against each other. That calm was shattered by the Syrian army's June 22 offensive, whose speed has surprised observers and outstripped aid agencies' response plans.

Although opposition negotiators insisted Tuesday that they have the support of the entire armed opposition in the southwest, it appeared likely that a number of groups would continue fighting even if a deal is struck.

The United Nations said Monday that some 164,000 people have been displaced to villages and makeshift camps in the Quneitra area, close to the Israeli-occupied Golan Heights. Tens of thousands more are spread out across the region. An additional 60,000 people have moved toward the Jordanian border, where a combination of meager resources and harsh weather has already caused some deaths. At least 12 children, two women and an elderly man have died of scorpion stings, dehydration or diseases transmitted through contaminated water, the United Nations said.

Civilians reached by phone along the Israeli and Jordanian borders Tuesday shared photographs of a sea of makeshift tents. Children with dirty faces sought shade under shrubs.

"People are sleeping anywhere they can. They can't hear the warplanes here, and they are just relieved to be safe," said Mohamed al-Hourany, an activist from the town of Musayfrah who has twice fled the government advance with his family. "We'll see if that holds."