  In the limit of extremely intense electromagnetic fields the Maxwell
equations are modified due to the photon-photon scattering that makes the
vacuum refraction index depend on the field amplitude. In presence of
electromagnetic waves with small but finite wavenumbers the vacuum behaves as a
dispersive medium. We show that the interplay between the vacuum polarization
and the nonlinear effects in the interaction of counter-propagating
electromagnetic waves can result in the formation of Kadomtsev-Petviashvily
solitons and, in one-dimension configuration, of Korteveg-de-Vries type
solitons that can propagate over a large distance without changing their shape.
