&gt;I suspect such a reduction would significantly inflate the size of your problem.<p>If Metric TSP and a more general TSP are both NP-complete then there is an algorithm in P to transform a general TSP to a Metric TSP. So, a reduction could inflate the size of the problem, but that inflation will not be significant relative to the most naive approach.<p>Here is a SE algorithm: <a href="http:&#x2F;&#x2F;cstheory.stackexchange.com&#x2F;a&#x2F;14049" rel="nofollow">http:&#x2F;&#x2F;cstheory.stackexchange.com&#x2F;a&#x2F;14049</a>