  We construct a canonical formulation of general relativity for the case of a
timelike foliation of spacetime. The formulation possesses explicit covariance
with respect to Lorentz transformations in the tangent space. Applying the loop
approach to quantize the theory we derive the spectrum of the area operator of
a two-dimensional surface. Its different branches are naturally associated to
spacelike and timelike surfaces. The results are compared with the predictions
of Lorentzian spin foam models. A restriction of the representations labeling
spin networks leads to perfect agreement between the states as well as the area
spectra in the two approaches.
