Image caption Matt Smith reprises his role as the Doctor for a second series

The sixth series of Doctor Who will open with a two-parter set in the US, the BBC has announced.

Scenes will be filmed in the Utah desert for a story set in the late 60s in which the Doctor, Amy and Rory find themselves on a secret summons to the Oval Office.

The episodes have been written by new series boss Steven Moffat and co-produced with BBC America.

Production starts in Cardiff this month with Matt Smith and Karen Gillan.

Alex Kingston will reprise her role as River Song.

Moffat said: "The Doctor has visited every weird and wonderful planet you can imagine, so he was bound to get round to America eventually.

"And of course every Doctor Who fan will be jumping up and down and saying he's been in America before. But not for real, not on location - and not with a story like this one."

It has been announced previously that series six has been split into two blocks, with the first airing on BBC One in spring 2011 and the second block showing in autumn 2011.