  The ambiguity of macroscopic description of light pressure on continuous
medium originates from the uncertainty of dividing the energy-momentum tensor
of electromagnetically excited matter into material and field parts or,
equivalently, the total acting force into pressure and deformation terms. We
show that although there exists a continuum of formally correct formulations,
one can adopt the appropriate form of the macroscopic field stress tensor that
allows unified description of pressure during elementary light-matter
interactions, such as reflection/refraction, absorption and nonlinear
conversion. The proposed expressions for the pressure force are simple,
convenient and compatible with the polariton momentum $\hbar \bf k$. The
corresponding electromagnetic momentum density (14) generalizes Rytov's
definition for right-handed and left-handed frequency dispersive media.
