The United States strongly condemned Saturday a series of missile strikes that killed dozens of people in Syria's second city Aleppo.
At least 37 people were killed and 150 wounded in missile strikes on the Tariq al-Bab district on Friday, according the Syrian Observatory for Human Rights.
"The United States Government condemns in the strongest possible terms the series of rocket attacks against Aleppo, most recently the attack using Scud missiles on an eastern district of the city," State Department spokeswoman Victoria Nuland said in a statement.
Just four days earlier, 33 people including 15 children were killed in a missile attack on the nearby district of Jabal Badro, said the Observatory.
Activists have reported the army's use of surface-to-surface missiles on various targets in northern Syria since late 2012.
Nuland called the series of vicious attacks "the latest demonstrations of the Syrian regime's ruthlessness and its lack of compassion for the Syrian people it claims to represent."
The spokeswoman also pointed to the brutality of the attacks to reiterate the administration of President Barack Obama's calls for President Bashar al-Assad to step down.
"The Assad regime has no legitimacy and remains in power only through brute force," Nuland said.
"Syrians across the country have demanded that Assad, and the architects of his violent campaign, step aside and allow a Syrian-led political transition to begin so that the rights of all Syrians can be respected, and the country can begin to rebuild.
"The United States sees no indication that the brave Syrian people fighting against this aggression will accept these regime leaders, with the blood of so many Syrians on their hands, as part of a transition governing authority."
Nuland also noted that the United States has stepped up its humanitarian aid "in close coordination" with Syrian activists amid spiraling violence, contributing $385 million to help displace Syrian refugees and citizens inside the country.
"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.
The Syrian National Coalition decided to boycott talks with world power after announcing plans to form a government to run "liberated areas" of Syria, in what analysts said was a bid to boost its credibility and win more support from the international community.