  We discuss a degeneracy between the geometry of the universe and the dark
energy equation of state $w_{\rm X}$ which exists in the power spectrum of the
cosmic microwave background. In particular, for the case with $w_{\rm X} < -1$,
this degeneracy has interesting implications to a lower bound on $w_{\rm X}$
from observations. It is also discussed how this degeneracy can be removed
using current observations of type Ia supernovae.
