Many have opinion that US had a bigger hand in Assange arrest but no credible proof.... Since, a rape can't garner an international and interpol arrest warrent in such a short span of time.
A US Website 'The Raw Story' comes up with an article showing relation between Assange arrest and US involvement. According to that article, one of Assange's rape accuser had ties with US's CIA.
Anna Ardin, one of the accusers, has been linked to a US-backed anti-Castro feminist group called the Las damas de blanco (the Ladies in White).