  It is shown that the quasilinearization method (QLM) sums the WKB series. The
method approaches solution of the Riccati equation (obtained by casting the
Schr\"{o}dinger equation in a nonlinear form) by approximating the nonlinear
terms by a sequence of the linear ones, and is not based on the existence of a
smallness parameter. Each p-th QLM iterate is expressible in a closed integral
form. Its expansion in powers of $\hbar$ reproduces the structure of the WKB
series generating an infinite number of the WKB terms. Coefficients of the
first $2^p$ terms of the expansion are exact while coefficients of a similar
number of the next terms are approximate. The quantization condition in any QLM
iteration, including the first, leads to exact energies for many well known
physical potentials such as the Coulomb, harmonic oscillator,
P\"{o}schl-Teller, Hulthen, Hyleraas, Morse, Eckart etc.
