By Luke Pachymuthu and Charmian Kok
Arriving in Singapore for meetings with UBS's management and board, Gruebel said: "Yes. Always." when asked by Reuters on Wednesday if he had the board's backing.
Gruebel was expected to ask the board to back plans for a radical overhaul of investment banking under his leadership at the meetings in Singapore, a plan sources said would be accelerated after the trading scandal.
London-based UBS trader Kweku Adoboli was charged on Friday with fraud and false accounting dating back to 2008 relating to the losses.
UBS said Adoboli concealed unauthorized speculative trading in equity index futures over the past three months by creating fictitious hedging positions in internal systems.
Gruebel said on Sunday he would bear the consequences of the trading loss that was discovered last week but did not want to quit, adding the affair would influence the future strategy of the investment bank.
UBS chairman Kaspar Villiger signaled he was not panicked by the scandal. Speaking outside UBS's Singapore offices, Villiger denied the bank was feeling the pressure from its shareholders, and said it was very solid.
Analysts said the bank would be under pressure to identify where risk oversight had failed, and UBS has launched an internal investigation under independent board member and former Morgan Stanley chief financial officer David Sidwell, who chairs UBS's risk committee.
Speaking to the London-based Independent newspaper, Nick Leeson, who brought down British investment bank Barings after losing $1.4 billion in unauthorized derivatives trading in 1995, said UBS shared responsibility for the loss because of its lack of oversight.
"The criminality is always with the individual trader. But the bank, with its incompetence and negligence in controlling what is going on, is complicit," Leeson told the paper.
The UBS executive board was meeting on Wednesday before its wider set of board members gather later this week. The meeting, one of four per year, has strategic changes to the investment bank on the agenda, said several sources with direct knowledge of the plans.
Formula One motor racing's Singapore Grand Prix, of which UBS is a major sponsor, takes place on Sunday.
UBS shares were up 1.0 percent at 1255 GMT, compared with a 0.3 percent lower European banking sector <.SX7P>. The stock is down 80 percent from its 2007 peak.
Whiel UBS is under pressure to scale down, ring-fence or even split off its investment banking business from its core wealth management unit to shield private clients, a source at the bank told Reuters the board will not be rushed into dumping investment banking following the rogue trades.
The bank was widely expected to speed up an overhaul of its investment bank that had been planned for announcement at a November 17 investor day. Big shareholders have signaled they could wait until then while the bank completed an internal investigation, another source at the bank said.
UBS's largest shareholder, Singapore sovereign wealth fund GIC, met the bank's management on Tuesday and said it had expressed its disappointment. It urged them to take firm action to restore confidence and wanted details of how the bank would tighten risk controls.
GIC, which has a 6.4 percent stake in UBS and has lost about 77 percent of its 11 billion Swiss franc ($12.4 billion)investment, said its view of the bank as well-capitalized remained unchanged.
Helvea analyst Peter Thorne said the board should stay focused on the strategic review performed in the summer rather than any knee-jerk reaction to the trading scandal before the details were clear.
"I would like to think they are focusing on how much capital they need, how many people to employ, and the size and scale they want at the investment bank," he said.
Gruebel was expected to scale back proprietary trading and fixed income, but not do away with them completely.
Politicians in Britain and Switzerland have renewed calls to separate riskier investment banking businesses from commercial bank operations.
The trading loss was a heavy blow to the reputation of Switzerland's biggest bank, which had been recovering from its near collapse during the financial crisis and a damaging U.S. investigation into its aiding wealthy Americans dodge taxes.
"Our near-term concern is the impact the recent turmoil will have on customer confidence in wealth management, which had been staging a gradual recovery in recent quarters," broker Collins Stewart said in a note. ($1 = 0.885 Swiss franc)
(Additional reporting by Saeed Azhar, Simon Webb and Martin de Sa'Pinto; Writing by Rachel Armstrong; Editing by Kim Coghill and Lincoln Feast)