U.S. President Barack Obama will formally demand that Syrian President Bashar al-Assad step down for power, according to a senior U.S. government official.

The Associated Press reported that Obama will issue a written statement on Thursday in which he will explicitly call for Assad to resign after his regime has conducted a brutal crackdown against anti-government protesters for the past five months.

Assad has used tanks and ground troops to seize control of parts of Syria where anti-regime activity has been concentrated.

Thousands of Syrians have fled into neighboring Turkey as refugees.

Secretary of State Hillary Rodham Clinton will subsequently make a statement about the dire situation in Syria, where thousands have been killed by government troops and many more have been arrested or disappeared.

The White House also plans to impose for sanctions on Syria.