Abstract: An extensible clasp or buckle for a wrist strap, which makes it possible to control the length of the wrist strap. The clasp has a first and a second strip which are articulated to one another at a first end, and a first tie which is arranged at a second end of the first strip for connection to a first strand of the wrist strap. The clasp also has a second tie which is arranged at a second end of the second strip for connection to a second strand of the wrist strap, and a way to displace the second tie with respect to the end of the second strip in order to adjust the length of the wrist strap. The second tie is connected to a cradle which is arranged in a housing located on the second strip. The housing has two opposite walls along which the cradle can slide. The clasp also has a tab which is connected to the second strip and arranged so as to cooperate with the cradle.