The present invention relates to an annular barrier to be expanded in an annulus between a well tubular metal structure and an inside wall of a borehole downhole for providing zone isolation between a first zone and a second zone of the borehole, comprising a tubular metal part for mounting as part of the well tubular metal structure, an expandable metal sleeve surrounding the tubular metal part, each end of the expandable metal sleeve being connected with the tubular metal part, an expandable space between the expandable metal sleeve and the tubular metal part, and an expansion opening in the tubular metal part through which fluid enters in order to expand the expandable metal sleeve, wherein the annular barrier further comprises a pressure-intensifying unit. The invention also relates to a downhole system comprising a well tubular metal structure and an annular barrier.