It's been revealed dozens of suspected Nazi war criminals and SS guards collected millions of dollars in US Social Security benefits after being forced out of the United States.

An Associated Press investigation has found the payments, underwritten by American taxpayers, flowed through a legal loophole that gave the US Justice Department leverage to persuade Nazi suspects to leave the US.

Among those receiving benefits were armed SS troops who guarded the network of Nazi camps where millions of Jews perished, a rocket scientist who used slave labourers to advance his research in the Third Reich, and a Nazi collaborator who engineered the arrest and execution of thousands of Jews in Poland.

There are at least four living beneficiaries.