WASHINGTON - The United States imposed sanctions on the Libyan government on Friday and said the legitimacy of longtime Libyan leader Muammar Gaddafi had been “reduced to zero.” In response to Gaddafi's crackdown on an uprising against his 41-year rule, President Barack Obama signed an executive order freezing the assets of Gaddafi, his family and top officials, as well as the Libyan government, the country's central bank and sovereign wealth funds. “These sanctions therefore target the Gaddafi government, while protecting the assets that belong to the people of Libya,” Obama said in a statement. “By any measure, Muammar Gaddafi's government has violated international norms and common decency and must be held accountable,” he added. The Obama administration had been criticized for its relatively restrained response so far to the turmoil. But US officials said fears for the safety of the Americans had tempered Washington's response. “(Gaddafi) is overseeing the brutal treatment of his people ... and his legitimacy has been reduced to zero in the eyes of his people,” White House spokesman Jay Carney said after Libyan security forces shot protesters in the streets of Tripoli on Friday. Obama discussed Washington's sanctions plan with the leaders of Britain, France and Italy on Thursday and Turkish Prime Minister Tayyip Erdogan on Friday. Canadian Prime Minister Stephen Harper said on Friday his government was preparing sanctions against Libya and that “Canada fully supports the United Nations Security Council on a resolution that could include a weapons embargo, individual sanctions against key Libyan officials and an asset freeze.” The US Treasury said the action would block substantial sums of Libyan money and prevent it being looted by the Gaddafi government, but declined to offer a dollar value. With the Libyan crisis also being taken up at the United Nations, European Union governments agreed on the idea of imposing an arms embargo, asset freezes and a travel ban on the oil-producing North African nation, with diplomats saying a formal decision would be taken early next week. Washington announced the sanctions move ��" along with the closing of its embassy and withdrawal of US diplomats ��" after a chartered ferry and a plane carrying Americans and other evacuees left Libya earlier on Friday.