Hezbollah on Saturday accused US-led forces of stranding a convoy of Islamic State fighters and civilians headed for Syria's Deir Ezzor province under an evacuation deal.
The convoy carrying hundreds of ISIS fighters as well as civilians was meant to travel from the Lebanon-Syria border to jihadist-held territory in eastern Syria under a deal Hezbollah helped broker.
But the US-led coalition has pounded the road to Deir Ezzor with air strikes to prevent the convoy reaching the ISIS-held town of Albukamal on the Iraqi border.
Hezbollah, which has defended the deal to remove ISIS fighters from the Lebanese frontier, said US-led forces had effectively stranded most of the convoy's 17 buses in the Syrian desert, beyond government reach.
"They are also preventing anyone from reaching them even to provide humanitarian assistance to families, the sick and wounded and the elderly," the Hezbollah statement said.
The convoy left the Lebanon-Syria border region on Monday, but Hezbollah said six of the buses remained in Syrian government-held territory.
"The Syrian state and Hezbollah have fulfilled their obligations to transfer buses out of the area of Syrian government control without exposing them," a statement by Hezbollah said Saturday, noting the buses that left government-held areas were no longer the responsibility of the Assad regime or its allies.
Hezbollah said there were old people, casualties and pregnant women in the buses stranded outside Syrian government control in the desert and called on the international community to step in to prevent them coming to harm.
A commander in the pro-Assad military alliance said earlier on Saturday that Hezbollah and the Syrian army were seeking an alternative way for the convoy to cross into Islamic State territory, having already tried two other routes.
"Work is under way to change the course of the convoy for a second time," the commander said.
About 300 lightly armed fighters were travelling on the buses, having surrendered their enclave straddling Syria's border with Lebanon on Monday under a deal which allowed them to join their jihadist comrades on the other side of the country.
The deal, brokered by Hezbollah with the support of its Syrian regime ally after a week-long offensive against ISIS, has been fiercely criticised by US-led forces and the Iraqi government.
The international coalition fighting ISIS has said it is unacceptable for jihadists to be transported to the border with Iraq, where pro-government forces this week ousted the extremist group from the northern city of Tal Afar.
The coalition has vowed to continue monitoring the convoy and disrupting any effort it makes to cross into jihadist territory but said it would not bomb it directly because it contains about 300 civilian family members of the fighters.
In a statement overnight, the coalition said it had sent a message to Damascus through Syria's ally Russia to say that "the Coalition will not condone ISIS fighters moving further east to the Iraqi border."
"The Coalition values human life and has offered suggestions on a course of action to save the women and children from any further suffering as a result of the Syrian regime's agreement," it added, without providing further details.
The coalition said it would not strike the convoy, but acknowledged hitting ISIS fighters and vehicles "seeking to facilitate the movement of ISIS fighters to the border area of our Iraqi partners."
Hezbollah accused US forces of hypocrisy, saying they had previously allowed ISIS fighters to flee territories in Iraq.
Iraqi Prime Minister Haider al-Abadi has described the deal as "unacceptable" and an "insult to the Iraqi people".
In Lebanon some criticized it for allowing fighters suspected of killing Lebanese citizens to escape on "air-conditioned buses."
Deir Ezzor in Syria's east is one of the jihadists' last remaining strongholds, where they hold most of the province and parts of its capital of the same name.
Reuters contributed to this report.