  We show that in the Standard Model the parametrically leading (by a factor
1/alpha_s) contribution to the inclusive CP asymmetry in B->X_{s,d}+gamma
decays arises from a long-distance effect in the interference of the
electromagnetic dipole amplitude with the amplitude for an up-quark penguin
transition accompanied by soft gluon emission. This contribution is governed by
a single hadronic parameter Lambda_{17}^u related to a matrix elements of a
non-local operator. In view of current experimental data, a future precision
measurement of the flavor-averaged CP asymmetry in B->X_s+gamma will signal the
presence of new physics only if a value below -2% is found. A cleaner probe of
new physics is offered by the difference of the CP asymmetries in charged
versus neutral B-meson decays.
