Display Screen or Portion Thereof with an Animated Graphical User Interface

FIG. 1 is a front view of a first image in a sequence of a display screen or a portion thereof with an animated graphical user interface, showing the novel design; and,

FIG. 2 is a front view of a second image thereof.

In FIGS. 1 - 2 the solid lines illustrate the claimed ornamental design. The outer-most broken lines illustrate a mobile device, which forms no part of the claimed design. The remaining broken lines illustrate portions of the display screen, and portions of the graphical user interface, and form no part of the claimed design. The stippling forms no part of the claimed design.