  We prove the existence of small amplitude, time-quasi-periodic solutions
(invariant tori) for the incompressible Navier-Stokes equation on the
$d$-dimensional torus $\T^d$, with a small, quasi-periodic in time external
force. We also show that they are orbitally and asymptotically stable in $H^s$
(for $s$ large enough). More precisely, for any initial datum which is close to
the invariant torus, there exists a unique global in time solution which stays
close to the invariant torus for all times. Moreover, the solution converges
asymptotically to the invariant torus for $t \to + \infty$, with an exponential
rate of convergence $O( e^{- \alpha t })$ for any arbitrary $\alpha \in (0,
1)$.
