More than five months after the beginning of Syria's popular uprising, Barack Obama dramatically increased the pressure on President Bashar al-Assad yesterday, uniting the western world behind a demand that the dictator step down from power and end the assault on his own people.
It was the first time that the United States had issued an explicit demand for Mr Assad to leave office.
The statement from Mr Obama, which comes at the end of a week that has seen the Syrian regime deploy gunships to shell protesters in the town of Latakia, was part of a co-ordinated action that saw similar moves from Britain, France, Germany and Canada, as well as the European Union and the United Nations.
"His calls for dialogue and reform have rung hollow while he is imprisoning, torturing and slaughtering his own people," the US president said. "For the sake of the Syrian people, the time has come for President Assad to step aside."
Perhaps more meaningfully, the statements were accompanied by a US executive order that bars American trade with Syria and puts drastic limitations on the money Mr Assad will be able to glean from oil and gas exports. More sanctions could follow soon.
Earlier yesterday, the United Nations said that Mr Assad had told UN Secretary-General Ban Ki-Moon, pictured left, that all military and police operations had stopped.
But there were still reports from the London-based Syrian Observatory for Human Rights that nine people had been shot dead by regime forces in the town of Homs as recently as Wednesday night.
Almost 2,000 people are estimated to have been killed by Syrian troops since March.
The US had apparently intended to make the statement last week, only to postpone after Turkey asked for more time to persuade Mr Assad to change course.
But as regional powers distanced themselves from the Syrian regime, the momentum for the co-ordinated denunciation rose after David Cameron and Mr Obama discussed the issue on Saturday, a Downing Street source said.