  Dissipative dynamics of a quantum bit driven by a strong resonant field and
interacting with a heat bath is investigated. We derive generalized Bloch
equations and find modifications of the qubit's damping rates caused by Rabi
oscillations. Nonequilibrium decoherence of a phase qubit inductively coupled
to a LC-circuit is considered as an illustration of the general results. It is
argued that recent experimental results give a clear evidence of effective
suppression of decoherence in a strongly driven flux qubit.
