US Ambassador to the UN Nikki Haley on Friday urged Russia to pressure its Syrian ally to uphold a ceasefire in southwest Syria following a surge of fighting in rebel-held areas.
Jordan, Russia and the United States agreed last year to set up a de-escalation zone for the region that includes Daraa, Quneitra and Sweida. The area borders Jordan and the Israeli-annexed Golan Heights.
"The Syrian regime's violations of the ceasefire in southwest Syria need to stop," said Haley in a statement.
"We expect Russia to do its part to respect and enforce the ceasefire it helped establish, and to use the influence it has to stop the Syrian regime's violations and any further destabilizing actions in the southwest and throughout Syria."
"Russia will ultimately bear responsibility for any further escalations in Syria," she added.
More than 11,000 people have been displaced in the upsurge of violence that has included air strikes, artillery, barrel bombs and rocket attacks, according to the US statement.
President Bashar al-Assad has set his sights on retaking rebel-controlled parts of southern Syria, whether through negotiations or a military operation, and has been amassing troops there in recent weeks.
Over the past three days, areas in eastern Daraa have been bombarded, forcing thousands of civilians to flee, according to the British-based Syrian Observatory for Human Rights.
Assad's forces have retaken large parts of Syria from opposition fighters since Russia intervened militarily on its side in 2015.
The UN Security Council is scheduled to discuss Syria on Wednesday.