  It is shown that the fusion of strings is a source of particle production in
nucleus--nucleus collisions outside the kinematical limits of nucleon--nucleon
collisions. The spectrum of different particles is compared with the high
energy data on p--A collisions obtaining a reasonable agreement. Results for
A--B collisions at $\sqrt{s}=19.4$ AGeV and $\sqrt{s}=200$ AGeV are given. It
is shown that the fusion of strings can accelerate particles up to the highest
energy detected in cosmic rays without help of any additional cosmic
accelerator. Also the rise of the average shower depth of maximun for cosmic
rays in the energy range between $10^{16}$ eV and $10^{19}$ eV can be explained
by the same mechanism without requiring any change in the chemical composition.
