A spokesman for the United States Grand Prix insists that construction work at the location of the new circuit being built near Austin, Texas is still on schedule despite the fact that work to clear the site has only just been completed.

The circuit is due to join the F1 calendar next season with progress being closely monitored after the new Korean venue was only just completed in time for its first race on the schedule late last year.

Organisers have taken steps to mark the layout of the circuit, which will feature extensive elevation changes and will mimic a number of top corners in F1, and despite the lack of any further visual progress, spokesman Jeff Hahn insisted everything was on schedule.

"Right now as it stands, all of our construction milestones are on track," he told KVUE News.

"It's an aggressive schedule. We are planning on a June 2012 opening day. Now it's not unusual. A lot of other tracks like this have been built in the same amount of time."