The White House branded Syrian President Bashar al-Assad's assault on his own people as "heinous and unforgivable" Thursday and called for a political solution rather than military action.
"That's why we're working with a broad array of international partners to isolate and pressure Assad, to bring around a peaceful transition in that country, a transition that is inevitable and already under way," spokesman Jay Carney told reporters traveling with President Barack Obama.
"The assault that Assad has waged against the Syrian people is heinous and unforgivable."
Asked if Obama had seen images of the violence in Syria, Carney replied: "I know he is fully aware, has been briefed on and read many news accounts about the atrocities committed by the Assad regime. It is the reason why he has so forcefully condemned it."
The remarks came after an international panel handed to the UN a list of Syrian officials suspected of crimes against humanity, and as the regime in Damascus ignored an outcry over the killing of two western journalists.
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Carney said he was unsure if Obama had seen television pictures of the violence gripping Syria but the president is "fully aware of the shameful cowardice that that behavior represents."
"We continue to believe that a political resolution is the best approach," Carney added, noting that arming Syrian rebels or other military involvement could "lead down a dangerous and chaotic path," though the United States will "have to evaluate this as time goes on."
The international panel said there had been a widespread and systematic pattern of gross violations committed by Syrian forces, "in conditions of impunity," since March 2011 when the uprising against Assad's regime erupted.
The report said Syria's government had "manifestly failed" to protect its people, but also said it had found instances of gross abuses committed by rebel fighters, many of them army defectors.
Fifty-two people were killed across Syria on Thursday, according to the London-based Syrian Observatory for Human Rights. The group says more than 7,600 people have been killed in the 11 months since the uprising began.
Activists spoke of "terrifying explosions" in the besieged city of Homs, as encircling troops pounded rebel areas for a 20th straight day.