Reading trough old Soviet newspapers I found that they often accuse USA in supporting Pol Pot regime. Now, I understand that you should take anything in Cold War era press, especially Soviet, with a bucket of salt, but on the other hand, Campuchia was anti-Soviet and anti-Vietnamise, and American support to pretty horrible regimes is not unheard of. What was the real relationship between USA and Campuchia.
The US foreign policy in many nations is never very easy to define. But they seemed to follow the idea of an 'the enemy of my enemy is my friend.'
For instance when Vietnam invaded, they used their alliance with Thailand to give support. Michael Haas sums it up nicely in his book on the two relations 'Cambodia, Pol Pot, and the United States: The Faustian Pact':
'The US public would never permit an open alliance with Pol Pot...Hence the Khmer Rouge became a Sino-Thai ally, a US ally twice removed.'
It would be bold to say the United States were a great supporter of the regime, but the Soviet report you read is not a work of fiction.
You can preview Michael Haas' book here free if you want to see more. http://books.google.co.uk/books?id=n1D7l8qUpN8C&pg=PA17&dq=pol+pot+usa&hl=en&sa=X&ei=DOoqU6iNI8qGkQXph4DADg&ved=0CC8Q6AEwAA#v=onepage&q=pol%20pot%20usa&f=false