Yen heads for biggest weekly drop since May despite Tokyo's support pledges

July 24 : The yen was on course for its steepest weekly decline since May on Friday, capping a turbulent stretch that has sent the currency to new 40-year lows versus the dollar despite Japan's pledges to stabilise the currency.Verbal efforts to support the yen have had limited effect, and some analysts believe even intervention would, at best, only buy policymakers some extra time. Unless the Bank of Japan raises rates more quickly, the structural forces weighing on the currency were likely to remain in place, they said.The U.S. Treasury Department joined calls for rate hikes by the BOJ on Thursday, warning that excessive currency volatility was undesirable. The yen's weakness left the U.S. dollar poised for a weekly gain of 0.88 per cent, which would be the biggest rise since May."We exp