NEW YORK, July 10 (Reuters) - U.S. 30-year Treasuries prices turned lower Thursday after relatively weak results at an additional sale of $13 billion worth of an existing 30-year bond, the last of this week's $61 billion in fixed-rate government debt supply.
On the open market, 30-year bond prices were down 6/32 with a yield of 3.368 percent, up nearly 1 basis point from late on Wednesday.
Before the Treasury Department released the results of the 30-year auction, 30-year bond prices were little changed on the day with a yield of 3.360 percent.
The latest 30-year bond supply fetched a yield of 3.369 percent, which was the lowest in 13 months but still came in 1 basis point higher than what traders had expected.
Overall demand for the 30-year issue introduced in May was below its long-term average. The bid-to-cover ratio was 2.40, lower than June's 2.69 which was the highest since February 2013.
(Reporting by Richard Leong; Editing by Chizu Nomiyama)