  Hadron inclusive spectra in pp collisions are analyzed within the modified
quark-gluon string model including both the longitudinal and transverse motion
of quarks in the proton in the wide region of initial energies. The
self-consistent analysis shows that the experimental data on the inclusive
spectra of light hadrons like pions and kaons at ISR energies can be
satisfactorily described at transverse momenta not larger than 1-2 GeV/c. We
discuss some difficulties to apply this model at energies above the ISR and
suggest to include the distribution of gluons in the proton unintegrated over
the internal transverse momentum. It leads to an increase in the inclusive
spectra of hadrons and allows us to extend the satisfactory description of the
data in the central rapidity region at energies higher than ISR.
