Sept 10 (Reuters) - Gold prices held steady near a one-week high on Thursday as the U.S. dollar weakened ahead of a policy decision by the European Central Bank due later in the day. * The ECB's growth and inflation projections to be published on Thursday will only show slight changes compared with the bank's June forecasts, Bloomberg reported on Wednesday. * The Bank of Canada on Wednesday held its key overnight interest rate steady at 0.25%, as expected, but left the door open for possible future changes to bond buying.