  We study experimentally the propagation dynamics and interaction of a pair of
mutually incoherent nematicons: spatial optical solitons in nematic liquid
crystals. In contrast to earlier studies, we consider a bias-free
liquid-crystal cell and compare the soliton interaction in copropagating and
counterpropagating geometries. We analyze the dependence of nematicon
interaction on input power and observe a direct manifestation of a long-range
nonlocal nonlinearity. Attraction of counterpropagating solitons requires
higher powers and longer relaxation times than that of copropagating nematicons
due to losses-induced power asymmetry of counterpropagating nematicons.
