(CNN) Calling the situation in Syria's Eastern Ghouta "a travesty," US Ambassador to the United Nations Nikki Haley admonished the Russian government Tuesday for "deception, hypocrisy and brutality" on behalf of President Bashar al-Assad.

"I would ask my Security Council colleagues to consider whether we are wrong when we point to Russian and Iranian forces working alongside Assad as being responsible for this slaughter," said Haley, who further accused the Russian government of exploiting UN ceasefire negotiations to help Assad advance his campaign against opposition forces.

"Russia cynically negotiated a ceasefire it instantly defied," she said.

But Haley -- known for delivering blistering remarks at the council, particularly against Russia -- reserved some of her strongest admonitions for her UN colleagues, who she reprimanded for not holding Russia and Syria accountable with a tougher ceasefire agreement and stronger condemnations of Assad and his allies.

"This is a travesty," said Haley. "This should be a day of shame for every member of this council, and it should be a lesson about what happens when we focus on fleeting displays of unity, instead of on what's right. "