"Putting our legacy litigation issues behind us, including those relating to RMBS, remains a key part of our strategy."
The Bank has now set aside a total of £6.7bn to cover litigation in the US.
It is expected to report its ninth consecutive annual loss in 2016 when its full year figures are released next month.
RBS said that further "substantial additional provisions and costs may be recognised and, depending on the final outcome, other adverse consequences may occur".
Howver it stressed that the duration and outcome of these investigations remain uncertain, including whether settlements may be reached.
Ross McEwan, RBS’s Chief Executive Officer, said: “Putting our legacy litigation issues behind us, including those relating to RMBS, remains a key part of our strategy. It is our priority to seek the best outcome for our shareholders, customers and employees.”
