The connection between euclidean and hamiltonian lattice QCD requires the use of asymmetric lattices, which in turn implies the necessity of two coupling parameters. We analyse the dependence of space-and time-like couplings g,, and g~ on the different lattice spacings a and aT in space and time directions. Using the background field method we determine the derivatives of the couplings with respect to the asymmetry factor ~ = a/a~ in the weak coupling limit, obtaining We argue that the sum of these derivatives has to be equal to b0 = 11N/487r 2 and determine the A parameter for asymmetric lattices. In the limit ~ ~ co all our results agree with those of A. and P. Hasenfratz.