We describe a formalism for solving the BFKL equation with a coupling that
runs for moments above a certain infrared cutoff. By suitably choosing matc
hing conditions proper account is taken of the fact that the BFKL diffusion
implies that the solution in the infrared (fixed coupling) regime depends
upon the solution in the ultraviolet (running coupling) regime and vice ver
sa. Expanding the BFKL kernel to a given order in the ratio of the transver
se momenta allows arbitrary accuracy to be achieved. (C) 2001 Published by
Elsevier Science B.V.