Barack Obama and John McCain enter their final week before the start of the US presidential nominating conventions amid intense speculation about who they plan to choose as their respective running mates – with Mr Obama almost certain to make his choice in the next few days.

Mr Obama, whose four-day Democratic convention starts next Monday in Denver, will this week attend election rallies and “town hall” meetings in the swing states of New Mexico, Florida, North Carolina and Virginia – any of which could provide a potential venue to announce his pick.