US Republican presidential candidate Mitt Romney has said that a video clip in which he called nearly half of Americans "victims" was "not elegantly stated" and was "spoken off the cuff."

He was also secretly taped saying that US President Barack Obama's campaign approach was "attractive to people who are not paying taxes."

Romney spoke to reporters on Monday evening at a hastily called news conference in Costa Mesa.

Obama's campaign quickly seized on the video, obtained by the magazine Mother Jones, and made it public, on a day that Romney's campaign conceded it needed a change in campaign strategy to gain momentum in the presidential race.

The Republican nominee did not disavow the comments but said they were made during a question-and-answer session.

He said it was indicative of his campaign's effort to "focus on the people in the middle."

Romney did not dispute the authenticity of the hidden-camera footage, but he called for the release of the full video, instead of the clips posted online.