Jun.12 (GMM) Sebastian Vettel's appearance on an iconic American talkshow went awry this week when David Letterman started talking about 'DRS'.

Letterman, the Indianapolis-born motor racing fan and Indycar team co-owner, began talking to the 24-year-old German and his 'Late Show' audience about F1's drag-reduction system.

"Complicated stuff," Vettel smirked as he explained the mechanics of the rear-wing overtaking flap.

Sebastian Vettel, Red Bull Racing
Sebastian Vettel, Red Bull Racing

Photo by: xpb.cc

Letterman then turned the conversation to the 'DRS' zones on the circuit, and the system's activation.

Vettel intervened: "Now you make it really complicated," he grinned. "The people here have no f*ing idea what you're talking about."

Producers not only had to bleep the swear word, Vettel's mouth was also blurred.

Realising his mistake, the Red Bull driver put his hand over his mouth and smiled: "Sorry."

But he let slip yet again when Letterman asked about New Jersey's 2013 street layout, which Vettel had sampled in an Infiniti road car earlier on Monday.

"It (the layout) looks very quick. You need some big balls I think," he grinned again, gesticulating towards his jeans.

When Vettel began speaking again, Letterman joked: "Just don't do that again, alright?

"I'm just glad Oprah doesn't have a show ..."