* U.S. stocks muster gains, curbing Treasuries appeal * Bonds fail to gain from ADP private sector job losses * Supply concerns continue to weigh on government debt (Updates prices, adds comment, reaction to ISM data, byline) By John Parry NEW YORK, March 4 (Reuters) - U.S. Treasury debt prices slid on Wednesday as stocks embarked on a tentative recovery from 12-year troughs hit this week, curbing the safe-haven bid for government debt as concerns about ballooning bond issuance also weighed down Treasuries. The benchmark 10-year Treasury note's yield, which moves inversely to its price, briefly rose above 3 percent, near a one-month high and more than one percentage point above five-decade lows hit in mid-December. In a hint that investors are becoming increasingly hardened to a diet of dismal economic data, Treasuries appeared to shrug off a hefty loss of private sector jobs reported on Wednesday. Such grim data usually boosts government bond prices. "The main offset to the impact of weak economic data is concerns about supply," said T.J. Marta, founder and market strategist with Marta on the Markets, a financial markets research firm in Scotch Plains, New Jersey. Government bond prices remained lower after a report showed a less-steep-than-expected contraction of the service sector. ADP said private employers cut 697,000 jobs in February, versus a revised 614,000 lost in January. Economists' median forecast for February private sector job losses was 610,000. The data is closely watched since the government will release its comprehensive U.S. employment report on Friday -- usually a big catalyst for financial markets -- which economists expect to show a loss of 648,000 nonfarm payrolls jobs in February, according to the median forecast. "For the Treasury market to improve we need to see a flight-to-quality play from equities or evidence that the recession is getting even worse than envisioned," said Kevin Flanagan, fixed income strategist for global wealth management with Morgan Stanley in Purchase, New York. The 10-year Treasury note traded down 31/32 in price for a yield of 3.0 percent, versus 2.89 percent late on Tuesday. "The 3 percent level will continue to be problematic in terms of being serious resistance for yields," said Marta, of Marta on the Markets. A major test of investor sentiment is likely to be the U.S. government's announcement, expected on Thursday, of issuance via next week's auctions of 3-year notes, 10-year notes and 30-year bonds, Marta added. The 30-year Treasury bond fell 1-20/32 in price for a yield of 3.70 percent versus 3.61 percent late Tuesday. Analysts expect the government to issue some $2 trillion of debt this year on top of the near $6 trillion Treasury market; a prospect which is tending to punish longer maturities most. Among shorter-dated debt, the 2-year note , which often benefits from a safe-haven bid when investors shun stocks and other riskier assets, slipped 4/32 in price for a yield of 0.96 percent, versus 0.89 percent late Tuesday. (Editing by James Dalgleish)

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