Sen. John McCain called Wednesday for sanctions and arrest warrants to be issued for Syria's President Bashar Assad and his inner circle, but said military intervention was not a solution to the crisis.
The former Republican presidential candidate spoke as the Syrian Observatory for Human Rights said it had collected the names of at least 453 civilians killed during almost six weeks of pro-democracy protests in Syria and the United Nations agreed to discuss how to end the violence.
The regime's crackdown appears to have only emboldened protesters who started their revolt with calls for modest reforms, but are now increasingly demanding Assad's downfall.
The U.N.'s Human Rights Council said Wednesday that would hold a special session on Syria Friday to try to stop Assad's forces from gunning down his people.
The U.S. requested the meeting, backed by council members Belgium, Britain, France, Hungary, Japan, Mexico, Norway, Poland, Korea, Moldova, Senegal, Slovakia, Spain, Switzerland and Zambia. The U.N. appealed Tuesday to Assad to withdraw his forces.
In an interview with Al-Jazeera television in Doha, Qatar, McCain said the world should offer its "moral support" to the protesters and also put pressure on the regime.
"I think we ought to impose the most severe sanctions possible," McCain told Al-Jazeera.
"I think it would be sanctions of every conceivable kind, including individual sanctions, not just Bashar but the circle of people around him, literally warrants for their arrest if they left the country and certainly freezing all their financial assets," he added.
The International Criminal Court should prosecute, McCain said, because "they are committing crimes against their own people."Video: In Syria, no easy way out (on this page)
He told Al-Jazeera that the U.S. had made "a big mistake" in 2009 when "the Iranian people rose up and we refused to give them moral support."
"These people deserve moral support in Syria," McCain told the TV station, adding they were "literally dying as we speak."
However he said he did not see any scope for action similar to that taken in Libya, where NATO jets are enforcing a no-fly zone and attacking Moammar Gadhafi's forces with the aim of protecting civilians on the ground.
"I don't see a military intervention as a solution (in Syria). I just don't see the scenario, so I don't support such a thing," McCain told Al-Jazeera.
Assad not a 'reformer'
He added that the U.S. should never have sent an ambassador to Syria "in this delusion that some how he (Assad) was a reformer."
Top stories: Turmoil in the Middle East
Amnesty International also urged the U.N. Security Council to refer the situation in Syria to the International Criminal Court.
"The Syrian government is clearly trying to shatter the will of those peacefully expressing dissent by shelling them, firing on them and locking them up," said Salil Shetty, Amnesty International's Secretary General.
Syrian opposition figures said Wednesday that their "massive grassroots revolution" would break the regime unless Assad led a transition to democracy.
The statement from an umbrella group of opposition activists in Syria and abroad called the National Initiative for Change said a democratic transition will "safeguard the nation from falling into a period of violence, chaos and civil war."
"If the Syrian president does not wish to be recorded in history as a leader of this transition period, there is no alternative left for Syrians except to move forward along the same path as did the Tunisians, Egyptians and Libyans before them," the statement said.
The opposition is getting more organized as the uprising gains momentum, but it is still largely a grassroots operation. There are no credible opposition leaders who have risen to the level of being considered as a possible successor to Assad.
On Monday, the army sent tanks into Daraa, 80 miles south of Damascus, and there have been reports of shooting and raids there and in areas across the country ever since. Daraa is where the uprising began last month.
Agents hunting people
On Wednesday, witnesses and human rights activists said the army also deployed tanks around the Damascus suburb of Douma and the coastal city of Banias, where there have been large demonstrations in recent weeks.
One Douma resident said security agents were going house-to-house, carrying lists of wanted people and conducting raids.
If the agents did not find the person they were looking for, they took his relatives into custody, the resident said. Two funerals were planned Wednesday, he added.
White buses brought in hundreds of soldiers in full combat gear into Douma, a witness told Reuters on Wednesday,
The witness, a former soldier who did not want to be identified, said he saw several trucks in the streets equipped with heavy machine guns and members of the plainclothes secret police carrying assault rifles. He believed the soldiers to be Republican Guards, among the units most loyal to Assad.
In Banias, a witness said the army redeployed tanks and armored personnel carriers near the main highway leading into the city.
Residents contacted by the AP spoke on condition of anonymity out of fear for their safety.
Syria has banned nearly all foreign media and restricted access to trouble spots since the uprising began, making it almost impossible to verify the dramatic events shaking one of the most authoritarian regimes in the Arab world.
Meanwhile, Syria's U.N. envoy said Tuesday that it was perfectly capable of conducting its own transparent inquiry into the deaths of anti-government demonstrators and needed no outside assistance.
"Syria has a government, has a state," Ambassador Bashar Ja'afari told reporters who asked about a call by U.N. chief Ban Ki-moon for an investigation. "We can undertake any investigation by our own selves with full transparency. We have nothing to hide."
The Associated Press and Reuters contributed to this report.