British insurer Aviva Plc and Turkey's Sabanci Holding have mandated Citigroup and HSBC to sell between 20 and 25 percent of Turkish life and pensions joint venture Avivasa Emeklilik & Hayat Sigorta in an initial public offering, two sources told Reuters on Friday.

The share sale is not imminent as it is the subject of a feasibility study, one of the sources close to the matter said.

Aviva, Citi and HSBC declined to comment. Sabanci was not immediately available to comment.

Sabanci and Aviva may sell shares towards the end of 2014, Haluk Dincer, head of retail and insurance at Sabanci Holding, said on March 28.

Aviva is in the midst of a group wide restructuring led by Chief Executive Mark Wilson who joined the firm at the end of 2012 from Asian rival AIA, selling off non-core businesses, cutting costs and improving profitability.

The revamp has involved top level management changes and in October the group sold its U.S. business for $2.6 billion