  We explore the possibility to observe hard exclusive three-jet production in
early LHC runs, corresponding to diffractive dissociation of the incident
proton into three jets with large but compensating transverse momenta. This
process is sensitive to the proton unintegrated gluon distribution at small x
and to the distribution of the three valence quarks in the proton at small
transverse distances. The corresponding cross section is calculated using an
approach based on k_t factorization. According to our estimates, observation of
hard diffractive three-jet production at LHC is feasible for jet transverse
momenta q_perp \sim 5 GeV.
