Condemning Syria's use of violence and intimidation against its people, the official said al-Assad "must put an end to the attacks on protesters, mass arrests and harassment" of citizens expressing rights and "must begin to introduce change."  The Syrian government has launched a clampdown on peaceful demonstrators since mid-March. The United Nations last week said as many as 850 people have died in the protests, and there have been thousands of arrests.  Along with al-Assad, the other senior Syrian officials are Vice President Farouk al-Shara, Prime Minister Adel Safar, Interior Minister Mohammad Ibrahim al-Shaar, Defense Minister Ali Habib Mahmoud, head of Syrian Military Intelligence Abdul Fatah Qudsiya and Political Security Directorate chief Mohammed Dib Zaitoun.  "As a result of this action, any property in the United States or in the possession or control of U.S. persons in which the individuals listed in the Annex have an interest is blocked, and U.S. persons are generally prohibited from engaging in transactions with them," the Treasury Department said in a statement detailing the steps.  The senior administration official said it's too early to estimate how much will be frozen.  "As I am sure you know, when we take actions obligatory for institutions to freeze, many institutions around the world might" do the same thing, the official said. "Amplifications around that may be significant."  Treasury also announced the designation of 10 individuals and entities under an executive order signed by Obama on April 29.  It targets Syrian officials and others "responsible for human rights abuses, including repression against the Syrian people, as well as a set of companies tied to Syrian corruption."
President Barack Obama Wednesday imposed tough sanctions against Syrian President Bashar al-Assad and six other senior Syrian officials in an effort to stop the regime's fierce crackdown on