  The total cross section of the reaction $pp\to ppK^+K^-$ has been determined
for proton--proton reactions with $p_{beam}=3.67 GeV/c$. This represents the
first cross section measurement of the $pp \to ppK^-K^+$ channel near
threshold, and is equivalent to the inclusive $pp\to ppK^-X$ cross section at
this beam momentum. The cross section determined at this beam momentum is about
a factor 20 lower than that for inclusive $pp\to ppK^+X$ meson production at
the same CM energy above the corresponding threshold. This large difference in
the $K^+$ and $K^-$ meson inclusive production cross sections in proton-proton
reactions is in strong contrast to cross sections measured in sub-threshold
heavy ion collisions, which are similar in magnitude at the same energy per
nucleon below the respective thresholds.
