A U.N. diplomat says Russia has blocked a Security Council declaration that would have criticized the Syrian regime's offensive against the rebel-held town of Qusair.

The Security Council diplomat says Russia blocked the declaration because the council made no statement when rebels seized the town. The diplomat spoke on condition of anonymity because the discussions Saturday were private.

Qusair has become a flashpoint in Syria's civil war, with the Lebanese militant group Hezbollah joining the regime's offensive. Syria's political opposition cited Hezbollah's role in the war and the dire situation in Qusair as reasons for not attending peace talks with the regime in Geneva.

Russia is a key ally of Syria and has vetoed three Western-backed resolutions aimed at pressuring President Bashar Assad to end the war.

Nobody was available for comment Saturday at Russia's U.N. mission.