UPDATE 1-RESEARCH ALERT-CIBC downgrades UBS, cuts '08 EPS view

(Adds analyst's comments, background; updates share movement)

Nov 19 (Reuters) - CIBC World Markets downgraded UBS AG (UBSN.VX) (UBS.N) to "sector performer" from "sector outperformer" and cut its 2008 earnings view for the Swiss bank by 33 percent, citing likely write-downs on credit exposures throughout the next year.

"We believe UBS will likely take roughly 8 billion Swiss francs in aggregate write-downs over the next five quarters but will do so by managing such against earnings from its Global Wealth Management division so as to not abruptly shock its capital base and therefore risk its highly coveted credit ratings," analyst Meredith Whitney wrote in a note to clients.

UBS reported its first quarterly loss in five years at the end of last month after writing down 4.4 billion Swiss francs ($3.92 billion) of subprime-linked exposures.

On Thursday, UBS doused speculation that it would book fourth-quarter write-downs in the order of $8 billion and said it did not yet know if it would take further charges in subsequent quarters.

CIBC's Whitney, who cut her 2008 earnings estimate for the bank to $3.85 a share from $5.75, said she expects earnings visibility to be much more difficult for UBS going into 2009.

Shares of UBS trade at 13.79 times estimated 2008 earnings, much higher than the broader European banking sector, which trades at an average of 8.22 times 2008 estimates.

"...We now believe there is little potential upside over the medium term for UBS shares," Whitney said.

A meltdown in U.S. subprime mortgages -- loans made to borrowers with patchy credit histories -- has triggered billions of dollars in charges for banks around the world on their exposures to bundles of mortgage-back securities.

Shares of UBS were trading down 2 percent at 51.90 Swiss francs by 0930 GMT. (Reporting by Tenzin Pema in Bangalore; Editing by Vinu Pilakkott)