This frame grab from video released on Monday and provided by the government-controlled Syrian Central Military Media, shows buses gathering before a planned evacuation of Islamic State group militants, in the mountainous region of Qalamoun, Syria. (Uncredited/AP)

The Lebanese Hezbollah movement on Saturday accused the United States of putting at risk the lives of women and children stranded on a convoy of Islamic State fighters that has been stuck in the Syrian desert for the past three days.

The accusation was the latest salvo in an escalating public relations battle between Hezbollah and the U.S. military over the fate of around 600 Islamic State fighters and their families who were permitted under a Hezbollah-brokered deal to leave an area in western Syria, near the Lebanese border, for an Islamic State-controlled town in eastern Syria.

Instead, the U.S. military on Wednesday intervened, having the road bombed ahead of the convoy, preventing it from reaching its destination, the town of Bukamal, near the Iraqi border.

The convoy of buses has since been stranded in the desert in Syrian government-held territory and is being monitored by the U.S. military, which has pledged to make sure it doesn’t reach Islamic State-held territory.

In a statement on Saturday, Hezbollah said the women, children, elderly, sick and wounded on board the bus are at risk of dying because U.S. warplanes are circling overhead, preventing the supply of food and water. It called on the international community to intervene to “prevent a terrible massacre.”

If the people in the convoy die because of bombing or lack of food, “full responsibility lies with the Americans,” Hezbollah said.

The U.S. military, however, has said it will not interfere if the government sends supplies to the convoy, and that the convoy has already received one delivery of food and water.

U.S. warplanes watched “someone” from the Syrian government side resupply the convoy with water and food two days ago and did not intervene, Lt. Gen. Stephen Townsend, the commander of the U.S.-led coalition, told reporters on Thursday.

“We’ve observed that. We didn’t try to interfere with that,” he said. “We have not tried to interfere with all approaches to the buses. And the pro-regime forces have done that and resupplied them.”

Still, Col. Ryan Dillon, serving as a spokesman, said the U.S. military intends to prevent the convoy from reaching Islamic State territory and will bomb any Islamic State vehicles that attempt to link up with it. But theconvoy itself won’t be bombed because of the presence of civilians, Dillon said.

Hezbollah has defended the deal to relocate the fighters from near the Lebanese border as necessary to save the lives of combatants and to secure the bodies of captured Lebanese army soldiers, Hezbollah fighters and an Iranian military adviser. The swap ended a week-long battle to eject the Islamic State from a remote stretch of territory spanning the Lebanese-Syrian border north of the Lebanese town of Ras Baalbek.

But the evacuation of the fighters to a location right on the Iraqi border triggered outrage in Iraq, which is preparing an offensive of its own to reclaim territory in the area. It has also been criticized in Lebanon, where opinion is polarized over Hezbollah's increasingly assertive role in directing the policies of the state. The smiling fighters, with automatic rifles slung over their shoulders, were seen sitting on the buses as they set out on the journey across Syria in photographs widely circulated on social media.

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Suzan Haidmous in Washington and Heba Habib in Stockholm contributed to this report.