Republican presidential contender Mitt Romney accidentally introduced Paul Ryan as the "next president" on Saturday.

Speaking at a rally in Norfolk, Virginia, Romney wrongly introduced the Wisconsin congressman.

"Today is a good day for America, and there are better days ahead. Join me in welcoming the next President of the United States, Paul Ryan," said Romney.

Romney did, however, quickly realise his error.

"Every now and then I'm known to make a mistake. I did not make a mistake with this guy, but I can tell you this, he's going to be next Vice President of the United States."

Romney's selection of Ryan as his running mate ends months of speculation.