Syria has accused the US of meddling after the American ambassador visited the flashpoint city of Hama ahead of planned anti-regime demonstrations. "The presence of the US ambassador in Hama without previous permission is obvious proof of the implication of the United States in the ongoing events, and of their attempts to increase (tensions), which damage Syria's security and stability," the foreign ministry said in a statement. "Syria warns against such irresponsible behaviour and stresses its determination to continue to take all measures that will bring back calm and stability to the country," it added after Robert Ford's visit.