Diageo will launch a mandatory share tender offer to buy up to 26 percent additional stake in United Spirits from public shareholders on January 7, the manager to the offer said in a notice to the Bombay Stock Exchange. Earlier this month, Diageo agreed to buy a majority stake in United Spirits, controlled by businessman Vijay Mallya, for $2.1 billion, fuelling a push by the world's biggest spirits group into fast-growing markets. [caption id=attachment_529359 align=alignleft width=434