  The strangeness $S=-2$ baryon-baryon interaction is studied in chiral
effective field theory up to next-to-leading order. The potential at this order
consists of contributions from one- and two-pseudoscalar-meson exchange
diagrams and from four-baryon contact terms without and with two derivatives.
SU(3) flavor symmetry is imposed for constructing the interaction in the $S=-2$
sector. Specifically, the couplings of the pseudoscalar mesons to the baryons
are fixed by SU(3) symmetry and, in general, also the contact terms are related
via SU(3) symmetry to those determined in a previous study of the $S=-1$
hyperon-nucleon interaction. The explicit SU(3) symmetry breaking due to the
physical masses of the pseudoscalar mesons ($\pi$, $K$, $\eta$) is taken into
account. It is argued that the $\Xi N$ interaction has to be relatively weak to
be in accordance with available experimental constraints. In particular, the
published values and upper bounds for the $\Xi^- p$ elastic and inelastic cross
sections apparently rule out a somewhat stronger attractive $\Xi N$ force and,
specifically, disfavor any near-threshold deuteron-like bound states in that
system.
