What does the US have to say about this?
Topic on Comments:UK to ban export of lethal injection drugs to US
I have not found any response from the US in any publications.
Here's a link that you might find to be helpful, albeit a bit unrelated: http://www.reuters.com/article/2011/04/01/us-executions-drug-idUSTRE7307ZK20110401
Very interesting! Thanks.