  If physics beyond the standard model is present in B decays, experimental
measurements seem to suggest that it principally affects those processes with
significant b->s penguin amplitudes. It was recently argued that, in general,
such new-physics (NP) effects can be parametrized in terms of a single NP
amplitude A^q and phase \Phi_q, for q=u,d,s,c. In this paper, we show that the
study of the decays Bs(t) -> K^+ K^- and Bd(t) -> \pi^+\pi^- allows one to
measure the NP parameters A^u and \Phi_u. We examine the implications for this
method of the latest experimental results on these decays. If NP is found in
Bs(t) -> K^+ K^-, it can be partially identified through measurements of
Bs(t)-> K^0 \bar K^0.
