  We calculate the cross sections for the $p(p,n\pi^{+})p$ and $p(p,p\pi^{0})p$
reactions for proton beam energies near threshold in a covariant
one-boson-exchange model, which incorporates the exchange of $\pi$, $\rho$,
$\sigma$ and $\omega$ mesons and treats both nucleon and delta isobar as
intermediate states. The final state interaction effects have also been
included. The $\omega$ meson exchange is found to contribute significantly at
these energies, which, along with other meson exchanges, provides an excellent
agreement with the data. The cross sections at beam energies $\leq$ 300 MeV are
almost free from the contributions of the $\Delta$ isobar excitation.
