  Nucleon-nucleon (NN) forces from chiral perturbation theory at
next-to-leading (NLO) and next-to-next-to-leading order (NNLO) are applied to
systems with two, three and four nucleons. At NNLO, we consider two versions of
the chiral potential which differ in the strength of the two-pion-exchange
(TPE) but describe two nucleon observables equally well. The NNLO potential
leads to unphysical deeply bound states in the low partial waves and effects of
the 3N forces, which appear first at this order, are expected to be large. We
provide arguments for a reduction of the TPE potential and introduce the NNLO*
version of the NN forces. We calculate nd scattering observables as well as
various properties of 3H and 4He with the NNLO* potential and find good
agreement with the data and with predictions based upon the standard
high-precision potentials. We find an improved description of the 3H and 4He
binding energies.
