The board of UBS reconvened its meeting on Saturday to decide the future of its scandal-hit investment bank and Chief Executive Oswald Gruebel after the Swiss bank lost $2.3 billion in alleged rogue trading.

The bank, which has lurched from crisis to crisis over the past three years, is under pressure to downsize or fence off risky trading activities in the investment bank and protect its core business of managing private investors' wealth.

After several days of meetings, the board left Singapore on Friday with some members headed back to Switzerland, sources told Reuters. Their deliberations continued on Saturday by conference call, another bank source said.

UBS's board meeting, one of four regular meetings per year, had originally been due to end on Friday ahead of the UBS-sponsored Singapore Formula One motor racing Grand Prix on Sunday, when executives will be trying to reassure big clients.

The Swiss newspaper Tages-Anzeiger cited an unnamed source familiar with the situation as saying the extension of the meeting meant there was probably a power struggle going on.

It is simply too early to say who wins, the source said.

The newspaper said the board had already taken a preliminary decision to focus the bank in future on wealth management and radically cut back on investment banking. A UBS spokesman declined to comment on details of the board meeting.

After the board ended its meeting for the day on Friday, a casually-dressed Gruebel -- a big motor racing fan himself -- declined to comment on his future.

Also in the firing line is investment bank boss Carsten Kengeter, whose attempt to rebuild the battered franchise was already stumbling even before the rogue trading scandal.

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Clients pulled nearly 400 billion Swiss francs ($442 billion) -- almost 20 percent of total client assets -- from UBS after the bank was battered in the financial crisis as well as a prolonged dispute with the U.S. tax authorities and the biggest annual corporate loss in Swiss history.

Under Gruebel's leadership, the bank's inflows have since turned positive but other private banks are now circling again to nab clients worried about reputational risk in the wake of the rogue trader affair.

The $2.3 billion loss allegedly caused by UBS trader Kweku Adoboli in unauthorized trades compares to the 4.9 billion euros ($6.6 billion) lost by rogue trader Jerome Kerviel at Societe Generale just three years ago, an event which prompted calls for tighter rules and felled that bank's then-chairman and CEO Daniel Bouton.

With his job now on the line, Gruebel, a former trader himself, wants board backing to keep him and his 'integrated banking' strategy -- maintaining the investment bank which he placed at the heart of UBS' recovery when he took over in 2009.

Former UBS CEO Peter Wuffli was ousted unceremoniously at a board meeting in Spain in 2007 to coincide with the America's Cup yachting event there, in which UBS was sponsoring a team.

UBS's largest shareholder, Singapore sovereign wealth fund GIC, met the bank's management earlier this week and in a rare public statement expressed its disappointment. It urged them to take firm action to restore confidence and wanted details of how the bank would tighten risk controls.

UBS lacks many heavyweight internal candidates to replace Gruebel after big management shakeups during the crisis, although it has been grooming Sergio Ermotti, former deputy CEO of Italy's UniCredit , since he joined in April.

(Reporting by Emma Thomasson; Editing by Ed Lane)

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