Russia called for urgent measures to ease the humanitarian crisis in east Ukraine on Tuesday but was bluntly told by the United States that it bore responsibility for the suffering.
Russia's appeal at the UN Security Council came amid a sharp increase in the number of refugees fleeing fighting in east Ukraine with 58,000 people driven from their homes over the past month alone.
"When addressing the humanitarian situation, we cannot lose sight of one underlying fact: Russia can stop all of this," US Deputy Ambassador Rosemary DiCarlo told the Council.
"The surest way to end the violence is for Russia to stop the flow of fighters, weapons and money from Russia into eastern Ukraine," she said.
Russia had called for the special meeting of the Council to hear top UN aid official John Ging who reported that the humanitarian situation was worsening in east Ukraine and that "immediate action" was needed.
Accusing Kiev of ignoring the plight of civilians, Russian Ambassador Vitaly Churkin described the situation in east Ukraine as "disastrous" and called for a humanitarian mission to be carried out by UN agencies.
"Russia calls on the international community to take emergency measures to improve the humanitarian situation in the east of Ukraine," said Churkin.
Responding to the appeal, the US deputy ambassador said UN agencies were already on the ground and working to help civilians who have been left without clean water, electricity and medical aid.
Russia and the United States have repeatedly clashed over the conflict in east Ukraine, with Washington accusing Moscow of backing the rebels who have taken arms against Kiev.
The US deputy envoy accused Russia of doubling the number of battalions on the border with Ukraine and stoking tensions with plans for military exercises.
"We again demand that Russia halt these destabilizing actions," said DiCarlo.
Ukrainian forces announced Monday they were closing in around the key city of Donetsk, after already scoring significant gains over the last month.
But the rebels have pledged to fight on in the cities under their control, and government forces continue to come under heavy bombardment from separatist positions.
At least 1,367 people have been killed and more than 4,000 wounded in the fighting in east Ukraine since mid-April, according to UN officials.