Former US President Bill Clinton, one of the architects of the subsidies to US farmers - and who is now, paradoxically, the co-chair of Haiti's earthquake recovery Commission - is quoted by Oxfam as saying that the policy was "a mistake".
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"It may have been good for some of my farmers in Arkansas, but it has not worked," said Mr Clinton, a frequent visitor to Haiti.
"I have to live every day with the consequences of the lost capacity to produce a rice crop in Haiti to feed those people, because of what I did."
The aid agency says the $434m (£274m) paid annually in domestic US rice subsidies is more than the total US aid to Haiti of $353m.
The Oxfam report said subsidies paid to American farmers meant the rice they export to Haiti - known locally as Riz Miami or "Miami Rice" - is cheaper than locally produced rice.
The foreign rice that is "dumped" in Haiti therefore exacerbates the rural-urban drift that has seen the population of the capital Port-au-Prince balloon out of control as farmers who cannot feed themselves move to the city in search of employment.