A clamping system for connecting a first and a second tube whose opposite ends have clamping surfaces protruding from the cylindrical outer surface of said tubes. The system comprises a collar which comprises a belt able to be clamped around said clamping surfaces, the belt having a first and a second flank between which an internal recess able to receive the clamping surfaces is delimited. The collar carries at least one retaining finger which has a free end portion protruding axially beyond the edge of the first flank, said free end portion having a retaining edge configured to be retained outside the belt by a radially protruding element.