We establish a close relation between the spatial string tension of the 3-dimensional SU (3) gauge theory at finite temperature ( σ s ) and the string tension of the 3-dimensional SU (3) gauge theory ( σ 3) which is similar to what has been found previously for SU (2). We obtain δ 3 =(0.554±0.004)g 2 3 and> δ 5 =(0.586 ± 0.045)g 2(T)T , respectively. For temperatures larger than twice the critical temperature, results are consistent with a temperature dependent coupling running according to the two-loop β-function with Λ T = 0.118(36) T c .