The Obama administration is expelling Syria's most senior envoy in Washington, joining a host of other governments in kicking out Syrian diplomats to protest last week's gruesome massacre in which entire families, including children, were shot execution-style in their homes.

The State Department said Tuesday that the charge d'affaires at the Syrian Embassy has been given 72 hours to leave the United States. Syria has not had an ambassador in the United States since the previous envoy left last year to take another post.

State Department spokeswoman Victoria Nuland said the U.S. holds "the Syrian government responsible for this slaughter of innocent lives."

Earlier Tuesday, numerous other western countries, including Australia, Britain, Canada, France, Germany, Italy, the Netherlands and Spain announced they were expelling Syrian diplomats.