Katherine Grainger: I've not been fast or good enough

Katherine Grainger and new partner Vicky Thornley finished sixth at the 2015 World Championships in France

British rower Katherine Grainger says winning Olympic gold at Rio in 2016 is realistic, but her recent performances have "not been good enough".

Grainger, 39, won gold at London 2012 in the double sculls with Anna Watkins.

With new partner Vicky Thornley she failed to win a medal at last month's World Championships in France.

"At the moment I am not fast enough, I'm not good enough. But absolutely it's about going to win in Rio," Grainger told BBC Radio 5 live.

Grainger returned to the sport in September 2014 after a two-year sabbatical following her Olympic success in 2012.

The Scot will be 40 by the time the Games in Rio start but claims she remains motivated by the challenges ahead.

Katherine Grainger won Olympic gold in the double sculls at London 2012 with Anna Watkins

"I didn't win a medal at the World Championships so I'm not yet where I need to be," Grainger added.

"But it was always a two-year plan and project, and I'm at the half-way point now.

"You shouldn't be in at this level unless you are in it to win it. If I didn't still have the hunger and desire then I wouldn't do it."