We study the non-existence of KAM tori for quasi-integrable, analytic Lagra
ngians. Let L: T-m x R-m --> R, L(Q, (Q)over dot) = 1/2 \((Q)over dot)(2) h(Q) and let <(omega)over bar> is an element of R-m be a frequency exponen
tially close to resonances. We find h analytic of norm arbitrarily small su
ch that L has no invariant torus of frequency <(omega)over bar> projecting
diffeomorphically on T-m.