LONDON--Royal Bank of Scotland Group PLC (RBS.LN) said Friday it is selling its internationally managed private banking and wealth-management business to Union Bancaire Privée UBP SA, for a price to be based on their assets under management on closing.

The bank, which is 80% owned by the U.K. government, said the sale includes client relationships outside the British Isles and associated staff. However, it will continue to service U.K. private banking and wealth-management clients" needs, together with those of international clients with a strong connection to the U.K., from the British Isles through its Coutts and Adam & Company brands.

At Dec. 31, 2014 assets under management of the business being sold were 32 billion Swiss francs ($33.38 billion) and total risk-weighted assets were CHF2 billion.

"Last year we set out a clear strategy to create a truly U.K.-focused bank. This announcement is another important step in that process," said Alison Rose, commercial & private banking chief executive.

RBS said it expects to book a charge of 200 million pounds ($298.52 million) in its first-quarter earnings, primarily relating to the goodwill write off.

The deal is expected to close in the fourth quarter of this year, subject to regulatory approvals.

Write to Ian Walker at ian.walker@wsj.com; @IanWalk40289749

Subscribe to WSJ: http://online.wsj.com?mod=djnwires