  We study theoretically the reconstruction of attosecond beating by
interference of two-photon transitions (RABBITT) in strongly polar molecules.
The time-dependent energy of a polar molecule in the infrared (IR) field gives
rise to an additional dipole-laser coupling contribution to the sideband delay.
In a time-independent picture this translates to the initial state becoming a
linear combination of IR-dressed states. We extend the recently developed
time-independent molecular R-matrix method to include the additional
interfering ionization pathways arising from the IR-dressed initial state and
obtain very good agreement with a reference non-perturbative time-dependent
RABBITT simulation. We discuss the asymptotic behaviour of such ionization
amplitudes and recover a known approximate asymptotic formula for the
dipole-laser coupling delay derived earlier in the context of attosecond
streaking. At low photon energies the dipole-laser coupling contributes
significantly even in an unoriented molecular sample. Finally, we show that in
photodetachment of polar singly charged negative ions the sideband delay is
asymptotically proportional only to Wigner delay.
