President Obama reached out to the leaders of Britain and Saudi Arabia on Saturday to build consensus for an end to the violent crackdown by Syria's government.

The White House said Obama spoke separately to British Prime Minister David Cameron and Saudi Arabia's King Abdullah, both of whom agreed with Obama that Syrian President Bashar Assad's government must end its attacks on civilians.

While the U.S. has repeatedly condemned the violence in Syria and said Assad has lost legitimacy, the Obama administration has stopped short of explicitly calling for him to leave power. A U.S. official told The Associated Press Friday that the demand for Assad to step down would come "sooner rather than later."

Some of the administration's hesitation reflects concern about adopting a more aggressive tone without adequate support from European allies and Arab partners.

The White House said Obama and Cameron agreed to closely monitor the actions the Syrian government and consult on further steps in the coming days. The Saudi king also agreed to consult with Obama closely, the White House said.

The U.S. issued new penalties against Syria last week, and Secretary of State Hillary Clinton has also called for a global trade embargo on oil and gas from the Middle East nation.

Anti-government protests in Syria have grown dramatically over the past five months, driven in part by anger over the government's bloody crackdown in which rights groups say at least 1,700 civilians have been killed.