* Benchmark yields remain in 1.8 to 1.9 percent range * Fed scheduled to buy longer-dated U.S. government debt * U.S. expected to raise debt ceiling but uncertainties remain By Chris Reese NEW YORK, Jan 23 U.S. Treasury debt prices rose marginally on Wednesday with support from safe-haven buying on worries over the pace of global growth and uncertainty as the United States is on track for divisive negotiations on spending cuts and the budget deficit. Treasuries were also lent support as the Federal Reserve is scheduled to buy $1.25 billion to $1.75 billion of longer-dated U.S. government debt as part of the central bank's latest economic stimulus program. Investors did some cautious buying in Treasuries on Wednesday after the S&P 500 and the Dow Jones industrial average reached five-year closing highs on Tuesday, with gains in equities stoked by a strong start to the corporate earnings season. Benchmark 10-year notes were trading 5/32 higher in price to yield 1.83 percent, down slightly from 1.84 percent late Tuesday. Yields have been relatively rangebound, holding between 1.80 percent and 1.90 percent for over a week. "Japan, Europe and the U.S. are struggling to find something more than 'surface growth,' and that is leading investors to hedge their hopes by taking some risk off the table in the form of U.S. Treasuries," said Kevin Giddis, managing director of fixed income at Morgan Keegan in Memphis, Tennessee. A proposed U.S. debt-limit extension is expected to be approved later on Wednesday, although the prospect of nearly four more months of uncertainty balanced out short-term relief at the measure. The extension of the debt limit to May 19 would prevent the United States defaulting on its debts in the short term, but was seen as prolonging the sense of uncertainty in markets. That uncertainty could filter through into economic data over coming months, supporting U.S. debt prices near current levels, as businesses put off investment decisions and consumers feel the hangover from the expiration of tax breaks. One big buyer of Treasuries was certain on Wednesday, with the Fed scheduled to buy Treasuries maturing February 2036 through November 2042. Ahead of that purchase, 30-year Treasury bonds were trading 6/32 higher in price with their yield little changed from late Tuesday at 3.02 percent.