UBS, the world's largest private bank, has agreed to buy PaineWebber, the fourth largest US private client firm, for about $12bn (€12.7bn), to bolster its presence in the fastest growing wealth management market in the world.

The deal, which has been recommended by the PaineWebber board and supported by its two largest shareholders, General Electric and Yasuda Mutual Life, will be a structured as a mix between cash, shares and debt.