The United States on Saturday condemned "in the strongest possible terms" the latest series of rocket attacks against Aleppo, specifically referencing the Scud missiles attack on Friday that killed several dozen people.
Also mentioning an assault on Aleppo on Tuesday, US State Department Spokesperson Victoria Nuland said in a press release: "These attacks, as well as other atrocities such as the strike against a field hospital earlier in the week, are only the latest demonstrations of the Syrian regime's ruthlessness and its lack of compassion for the Syrian people it claims to represent."
Nuland stated that the Assad regime "has no legitimacy and remains in power only through brute force."
"We look forward to meeting soon with the leadership of the legitimate representative of the Syrian people, the Syrian Opposition Coalition, to discuss how the United States and other friends of the Syrian people can do more to help the Syrian people achieve the political transition that they demand and that they deserve," she added.
Over the weekend, Russian Foreign Minister Sergei Lavrov accused the United States of having double standards on Syria, saying it had blocked a UN Security Council statement condemning a car bomb attack in Damascus.
Washington denied it had blocked the statement and said it had only asked for balance. The disagreement was likely to sour the atmosphere before Lavrov meets newly appointed US Secretary of State John Kerry next week in Berlin.
Lavrov told a news conference Washington had disappointed Moscow by blocking a statement condemning "terrorist attacks" near the Russian embassy in Damascus that killed more than 50 people and that Washington was threatening international unity in the "war on terror."
"We believe these are double standards," Lavrov said after talks with China's foreign minister.
"And we see in it a very dangerous tendency by our American colleagues to depart from the fundamental principle of unconditional condemnation of any terrorist act, a principle which secures the unity of the international community in the fight against terrorism," he said.
A spokeswoman for the US mission at the United Nations said it had not blocked any statement of condemnation but had sought to balance the text with criticism of Syrian President Bashar Assad's forces, which it said Russia had rejected.
"We strongly condemn all indiscriminate terrorist attacks against civilians or against diplomatic facilities," said Erin Pelton, spokeswoman for the US mission.
Ties between Washington and Moscow have worsened since Vladimir Putin returned to Russia's presidency last May.
The passage of US legislation intended to punish Russian officials accused of human rights abuses and a Russian ban on American families adopting Russian children have also contributed to the deterioration in recent weeks.