WASHINGTON (AFP) – US President Barack Obama said he was “appalled” by Syria’s crackdown on Sunday, which activists say killed nearly 140 people, and vowed to step up pressure to isolate President Bashar al-Assad.

In a statement, Obama saluted demonstrators who have taken to the streets as “courageous” and said Syria “will be a better place when a democratic transition goes forward.”

“I am appalled by the Syrian government’s use of violence and brutality against its own people. The reports out of Hama are horrifying and demonstrate the true character of the Syrian regime,” Obama said.

Senior Republican Senator John McCain accused Syrian authorities of carrying out a “massacre” and told AFP “I hope that there will be a move to bring charges to the International Criminal Court. It’s getting to that point.”

Human rights groups said that Syrian forces killed nearly 140 people on Sunday — including 100 when the army stormed the flashpoint city of Hama — as Assad crushed dissent on the eve of the Muslim holy month of Ramadan.

“In the days ahead, the United States will continue to increase our pressure on the Syrian regime, and work with others around the world to isolate the Assad government and stand with the Syrian people,” Obama said.

The Obama administration has repeatedly said that Assad has lost legitimacy while stopping short of explicitly seeking to oust him. The United States and its allies are already busy with a military campaign against Libyan strongman Moamer Kadhafi along with commitments in Afghanistan and Iraq.

“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,” Obama said.

“Through his own 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 its future. Syria will be a better place when a democratic transition goes forward,” Obama said.