  We use cosmological simulations of reionization to predict the possible
signal from the redshifted 21 cm line of neutral hydrogen in the
pre-reionization era and to investigate the observability of this signal. We
show that the separation of the mean (global) signal over the whole sky from
the known foreground contamination may be feasible, but very challenging. In
agreement with previous studies, we demonstrate that measuring angular
fluctuations in the HI signal is likely to be extremely difficult if not
impossible because of the overwhelming contamination from the galactic and
extragalactic foregrounds. However,we show that the sharp HI fluctuations in
the frequency domain should be easily separable from the relatively smooth
spectra of the foregrounds, and that these fluctuations should be detectable
even at moderate angular resolution (10-20 arcmin).
