Tensions between Egypt’s ruling generals and the U.S. government flared over the weekend after Cairo said it had barred at least a half-dozen Americans from leaving the country. The detained Americans include Sam LaHood, son of Ray LaHood, who is the U.S. secretary of transportation. In response, the Obama administration threatened explicitly to withhold its annual aid to the Egyptian military. “It is the prerogative of Congress to say that our future military aid is going to be conditioned on a democratic transition,” said Michael H. Posner, an assistant secretary of state responsible for human rights issues. State Department officials said that it was the first time in three decades that the $1.3 billion in annual American military aid to Egypt was at risk. Meanwhile, lobbyists for the Egyptian government in Washington including the Livingston Group, ended their contracts with the country. LaHood and the five others work for the International Republican Institute or its sister organization, the National Democratic Institute, whom Egypt has blocked from leaving as part of a criminal investigation into their activities. An Egyptian military team will visit Washington this week in an effort to clam tensions.