The problem of reconstruction of the 3D velocities of clusters of galaxies from the redshift distribution of galaxies of the cluster is formulated. By the first step the physical cluster is extracted among the galaxies appearing on the cluster 2D image. Though numerical simulations show the impossibility of direct use of Ambartsumian's formula derived for the stellar systems because of the small number of objects in the clusters, an additional physical assumption on the form of the searched velocity distribution can lead to the possibility of obtaining the transverse velocity of the cluster. The accuracy of the proposed reconstruction procedure is estimated.