Finance minister George Osborne is due to receive a final report from Treasury officials this week recommending against the most radical option mooted for the bank, the Sunday Times said.
Instead, RBS would be forced to commit to getting rid of tens of billions of pounds (dollars, euros) of problem loans more quickly, before the government begins selling off part of its 81-percent stake starting late next year.
Sky News also reported that Osborne will finalise his plans for the future of RBS this week, following recommendations made by investment bank Rothschild which focus on "internal surgery" rather than a wholesale break-up of the group.
RBS is due to release its third quarter results on Friday.
A spokeswoman for the Treasury told AFP she could not comment on the reports.