Washington: The US has significantly hardened its tone against Syrian regime, saying the images coming out of the Arab state are "grotesque and appalling" and it views President Bashar al-Assad as the cause of instability there.

"We are looking at ways to increase the pressure. The images coming out of Syria of the Syrian government's brutality against its own people have been grotesque and appalling, and they demonstrate the true character of the regime," White House Press Secretary Jay Carney said at his daily news conference.

"Once again, President Assad has shown that he is completely incapable and unwilling to respond to the legitimate grievances of the Syrian people. His use of torture, corruption, and terror puts him on the wrong side of history and his people," he said.

Carney said Assad is not "indispensable" and the US has nothing "invested" in him remaining in power.

"We do not want to see him remain in Syria for stability’s sake, and rather, we view him as the cause of instability in Syria.

"Through his actions, Bashar al-Assad is ensuring that he and his regime will be left in the past, and that the courageous Syrian people who have demonstrated in the streets will determine Syria’s future," he said. M The spokesman said the US supports Syrians fight for democratic reforms.

 "We want to see the Syrian people’s desire for democratic transformation carried out. We will continue to call on the regime to immediately halt its campaign of violence and arrests, pull its security forces back, release the many thousands of detainees, and to respect and act upon the clear demands of the Syrian people for a peaceful and democratic transition to democracy," Carney said.

On Tuesday, Secretary of State Hillary Clinton had met Syrian dissidents.

"We continue to press our message both to Asad, his regime, and to our partners throughout the world that the time for democratic change is already underway in Syria, and Asad has lost legitimacy in the eyes of his people and needs to allow that transition to take place," State Department spokesman Mark Toner said.

The US will continue to seek ways to isolate Asad and to reduce their access to revenue.

"We’re going to look at further sanctions and actions that can be taken to accomplish those goals. We’re going to continue our discussions in New York, and as the Secretary said, she believes strong action on the part of the council is long overdue on Syria," he said.

Toner said: "We are going to continue to make that case. Within Syria, we’re going to continue to meet with the opposition and to get a better sense of their direction."