The lender told investors it would hold a general meeting on Feb. 6 to vote on the plan.

RBS is 62.3 percent owned by British taxpayers, after a 45 billion pound bailout during the financial crisis.

Chief Executive Ross McEwan has made returning the lender to private hands a top priority during his tenure at the bank.

But the process has been slow due to turbulent markets and criticism from opposition politicians at losses incurred.

The last two sales of state-owned stock crystallised combined losses of more than 3 billion pounds.

Further losses are all but inevitable. Although RBS stock closed 1 percent higher on Thursday at 237 pence after the buyback plan announcement, it is still far below the 502 pence level it was trading at when it was bailed out in 2008.

RBS said a share buyback would help accelerate the process.

"This resolution would provide the bank with the flexibility to use some of its excess capital to buy back government shares at a time and price agreed with HM Treasury," Chairman Howard Davies said.

He said the board believed it was in the best interests of the bank and shareholders to facilitate a return to private ownership.

"The government should not be in the business of owning banks, which is why we're committed to returning RBS back to private ownership. But we will only sell RBS shares when it represents value for money to do so," a Treasury spokesman said.

The share buyback will be one of the first big tests of the bank's new chief financial officer, Katie Murray, who started the role in January.

RBS was left with 4 billion pounds of excess capital after it resolved a long-standing legal dispute with U.S. regulators last year over past mis-selling of toxic mortgage-backed securities in the run up to the financial crisis.

Analysts have said a state sale of RBS stock is unlikely until there is clarity about Britain's departure from the European Union, which they say is needed to calm markets.

RBS will announce full-year results for 2018 on Feb. 15.

(Reporting by Iain Withers; Additional reporting by Lawrence White; Editing by Sinead Cruise and Edmund Blair)

By Iain Withers