  We update the determination of |V_us| using semielectronic and semimuonic
decays of K mesons. A modest improvement of 15% with respect to its present
value is obtained for the error bar of this matrix element when we combine the
four available semileptonic decays. The combined effects of long-distance
radiative corrections and nonlinear terms in the vector form factors can
decrease the value of |V_us| by up to 1%. Refined measurements of the decay
widths and slope form factors in the semimuonic modes and a more accurate
calculation of vector form factors at zero momentum transfer can push the
determination of |V_us| at a few of percent level.
