Diplomats at the United Nations Security Council say Russia has blocked a declaration expressing concern about the situation in the besieged Syrian city of Qusair.
Rebels took over Qusair 18 months ago and government forces began an attack two weeks ago. Residents are trapped with little food, water or medicine.
The rebels are pleading for military help and medical assistance.
The BBC reports a draft statement circulated by Britain voiced concern, especially about the impact of the siege on civilians.
But diplomats said Russia will not support it because the UN failed to speak out when Qusair was seized by rebels.
Fighting in Qusair intensified last month with fighters from Hizbollah joined forces loyal to President Bashar al-Assad.