Method of welding a strip for the production of flexible tubular bodies made of plastic, comprising the following steps: shaping of a strip (1) around a welding rod; contacting of the ends (3, 4) of the strip; formation of a welded zone (5) by heating and compressing said ends (3, 4) and then by cooling them, said method being characterized in that the strip (1) is also heated outside the welded zone (5).