UK short sterling futures -- a gauge of market interest rate expectations -- rose after Bank of England governor Mervyn King said in a letter to the Chancellor of the Exchequer that raising interest rates now would put the economy at risk.The open letter of explanation to the Chancellor Alistair Darling was triggered after data Tuesday showed annual CPI inflation rising by more than one percentage point above the BoE's 2.0 percent target, with the May rate at 3.3 percent.King said inflation will run above target well into 2009 and that he expects to write several more letters to Darling over the next year. He poured cold water, however, on market expectations that UK interest rates would rise to counter rising inflationary pressures."If the bank rate were set to bring inflation back to target within the next 12 months, the result would be unnecessary volatility in output and employment," he said in the letter.He also noted a risk that the economic slowdown could be so sharp it would pull inflation down below the 2 percent target.