An assembly for producing sealed packaging units (14) from a sheet packaging material, comprises: an advancement device (21) for advancing the sheet packaging material along an advancement direction (F), a longitudinal sealing device for sealing opposite borders of the sheet packaging material along a longitudinal sealing band arranged parallelly to the advancement direction (F), thereby forming acontinuous tube (15), a transverse sealing device (29) for sealing the continuous tube (15) transversely to the advancement direction (F), so as to define a sealed packaging unit (14). The transversesealing device (29) comprises a sealing element (30) and an abutment element (31) that are intended to mutually cooperate during sealing while being located on opposite sides of the continuous tube (15). The sealing element (30) is so configured as to act on a side (27) of the continuous tube (15) on which the longitudinal sealing band is provided.