Thousands of protesters gathered outside the White House Saturday to demand that the United States "stop the massacre inSyria," where an estimated 8,000 people have been killed in a regime crackdown.

Wearing T-shirts declaring "I have a dream of a free Syria" and "No longer afraid," the demonstrators -- who numbered 4,000, according to organizers -- were marking the first anniversary of a bloody revolt against President Bashar al-Assad's regime.

Many of the protesters were Syrian Americans, and children participated in the demo.

"We want the world to do more, it cannot sit and watch people being slaughtered," said Basel al-Char, an Activists for a Free Syria organizer.

He said Assad, whose family has ruled Syria for four decades, should be sent to the International Criminal Court in The Hague.

"The world has been giving too many chances (to Assad) and it's only getting worse. We want them to support the Free Syria Army" made up of anti-regime dissidents, Char added.

Waving giant Syrian flags with three red stars over green, white and black stripes -- the so-called "Flag of Independence" in use intermittently in the 1930s-1960s and since used again by the opposition -- the protesters repeated at length "Bashar has to go" and "SOS, SOS."

Shaker Rashid said he came from the midwestern state of Indiana with his family and friends to "support the Syria revolution for the strive for freedom to bring down the Assad dictatorship."

Another protester, Abu Ramy, trampled on Chinese and Russian flags to express his anger after the countries vetoed UN Security Council resolution condemning the brutal crackdown.

Back in New Orleans, where he lives, Abu Ramy vowed he would burn the flags.

He pointed to a poster with US President Barack Obama's photograph that read "Syrian lives are in your hands."

"Every time Obama talks (about Syria), he's giving Assad a green light to continue the killings," Abu Ramy said.

Mazen Shoukfeh, of Detroit, Michigan, agreed.

"All we can do is apply pressure. In this country, people vote and the elections are around the corner," Shoukfeh said in a warning to Obama and Republican presidential candidates ahead of November 2012 ballots.

He held up a banner that read "Washington: enough talk, let's act. Stop the massacre in Syria."