TREASURIES-Prices jump after unexpectedly big downward U.S. GDP revision

* Data raise questions about U.S. growth

* Long bonds post biggest price gains

* Iraq fighting adds to gains

NEW YORK, June 25 (Reuters) - U.S. Treasuries prices jumped on Wednesday after government data showed the U.S. economy took a much worse bruising in early 2014 than previously calculated. Despite more recent economic reports illustrating good growth, yields on 30-year Treasuries fell to 3.371 percent from Tuesday's closing 3.403 percent. Thirty-year prices, which were already up on buying by investors rattled by fighting in Iraq, were up 22/32. Benchmark 10-year notes were up 13/32 to yield 2.541 percent, versus 2.58 percent late on Tuesday. The yield touched a low of 2.529 percent shortly after the U.S. revision of gross domestic product during January, February and March. "The GDP numbers were worse than expected, and that's in boldface and capital letters," said strategist Lou Brien at DRW Trading in Chicago. America's GDP fell at a 2.9 percent annual rate, the economy's worst performance in five years, instead of the 1.0 percent drop it had reported last month, according to the U.S. Commerce Department. "This means the Fed the next time it forecasts will have to revise downward its 2014 estimates," Brien said. "It just makes them look silly." Brien said softness in consumer spending, which accounts for more than two-thirds of U.S. economic activity, was especially worrisome. It increased at a 1.0 percent rate but had been previously reported to have advanced at a 3.1 percent pace. Economists estimate severe weather could have slashed as much as 1.5 percentage points from GDP growth in the first quarter. The government, however, gave no details on the impact of the weather. The government also reported on Wednesday that orders for long-lasting U.S. manufactured goods unexpectedly fell in May, another counter to hopes a strong rebound in growth is under way. Prices of shorter-maturity Treasuries rose more modestly than longer-dated issues but the asset group as a whole was also getting a lift along with other global debt from jitters over Iraq, investors said. "Iraq tensions have overshadowed relatively good economic data this week," said Lorne Baring, managing director of B Capital Wealth Management in Geneva. "Investors are still concerned about American foreign policy and what will be the next step in terms of any military intervention as opposed to diplomacy in the Middle East region." Militants attacked one of Iraq's largest air bases as the first U.S. teams arrived to assess the Iraqi security forces and decide how to help counter a mounting Sunni insurgency. Advances half years after the withdrawal of U.S. troops.

(Reporting by Michael Connor; Editing by James Dalgleish)