  We use the assumption of electric-magnetic duality to express the heavy quark
potential in QCD in terms of a Wilson Loop $W_{eff}(\Gamma)$ determined by the
dynamics of a dual theory which is weakly coupled at long distances. The
classical approximation gives the leading contribution to $W_{eff}(\Gamma)$ and
yields a velocity dependent heavy quark potential which for large $R$ becomes
linear in $R$, and which for small $R$ approaches lowest order perturbative
QCD. The corresponding long distance interaction between color magnetic
monopoles is governed by a Yukawa potential. As a consequence the magnetic
interaction between the color magnetic moments of the quarks is exponentially
damped. The semi-classical corrections to $W_{eff}(\Gamma)$ due to fluctuations
of the classical flux tube should lead to an effective string theory free from
the conformal anomaly.
