UBS is under pressure to overhaul its business after more than $37 billion in write-downs during the credit turmoil. UBS has appointed Lazard, the financial advisory group, to help undertake a review of its business.

Considering a sale of Paine Webber, the broker it bought nearly eight years ago for about $10 billion as a bridgehead into North America, is part of a review which is due to be concluded by October.

"If you are going to be a global wealth manager, then the US is a market where you have to be present. But it is also the case that you have to make it more profitable. is always an option," one of the sources told Reuters.

Another source said Paine Webber was "one of the assets that would be of serious interest to other people. If you were to merge Paine Webber with another brokerage, for example, there would be huge cost synergies," he said.

When Wachovia, the US bank, bought broker AG Edwards for $6.4 billion last year, it paid roughly $1 million per broker. A similar valuation for Paine Webber would value it at more than $8 billion.