  The backgrounds due to the direct diffractive dissociation of the photon into
the $\pi^+\pi^-$ as well as $K^+K^-$ pairs to the "elastic" diffractive $\rho
'$ and $\phi $ mesons production in electron-proton collisions are calculated.
It is shown that the role of background and background-resonant interference
contributions is very important in experimental distribution of $M_{\pi^+
\pi^-}$ in the $\rho '$ mass region. The amplitude for the background process
is proportional to the $\pi$-meson - proton or K-meson - proton cross sections.
Therefore, describing the HERA data, one can estimate $\sigma (\pi p)$ and
$\sigma (Kp)$ at energies higher than the region of direct measurements.
