The authors have defined approximation error for harmonic functions in DR, 0 < R < 00 the cJass of ali harmonic functions H in R3, that are regular in the öpen hail DR of radius R centered at the origin and are continuous on the closure DR of DR . Necessary and sufficient conditions, in terıns of the rate of decay of the approximation error En (H, R), such that II G DR has analytic continuation as an entire harmonic functions haviııg (p, q) -order p and (p, q)- type T, have been obtained.