* Bank of Japan steps up asset purchases to boost economy * Surprise jobless claims jump comes before key payroll data * JGB 10-year yields hit record lows, outperform Treasuries * U.S. 30-year bond yield breaks below 3 pct By Richard Leong NEW YORK, April 4 (Reuters) - The U.S. Treasury debt market rallied on Thursday as investors sought higher-yielding dollar assets after the Bank of Japan said it would step up asset purchases to boost its economy, sending Japanese bond yields to record lows. A surprise jump in domestic jobless claims undermined recent optimism about an improving labor market and fueled bets the Federal Reserve would cling to its own large-scale asset purchase program this year to cut unemployment, analysts said. The latest weekly jobless claims, which climbed to the highest since November, spurred concerns about the economic outlook in the second quarter and helped drive a safe-haven bid for Treasuries. These factors, together with lingering worries about the euro zone debt crisis, propelled a wave of bond buying that sent the yield on the 30-year Treasury bond below 3 percent for the first time since mid-January. "It's a sign that the quantitative easing cycle is very entrenched and it's expanding in other parts of the world," Garth Friesen, co-chief investment officer at III Associates, a hedge fund based in Boca Raton, Florida, said of Bank of Japan's asset purchase plan. "This is favorable for dollar-denominated assets." The benchmark 10-year Treasury note last traded up 15/32 in price at 102-4/32, yielding 1.763 percent, down 5.3 basis points from Wednesday. The 10-year yield encountered chart resistance in the 1.75 percent area, near its 200-day moving average. The 10-year U.S. Treasury note underperformed the 10-year Japanese government debt whose yield fell to a record low of 0.425 percent in reaction to the Bank of Japan's scheme to buy 7 trillion yen ($73 billion) in assets a month. PLUNGING DEEPER INTO THE QE POOL The Bank of Japan's move, worth $1.4 trillion, to jumpstart the world's third biggest economy is seen as risky, akin to the Fed's own bond-buying program currently at $85 billion a month. The BoJ is on track to expand its balance sheet at a monthly clip of 1.25 percent of its gross domestic product, or 15 percent of GDP this year. This compares with the Fed's current bond purchases, dubbed QE3, which is equivalent to 7 percent of the U.S. GDP this year, according to analysts. A main goal of central banks buying assets is to lower long-term borrowing costs and stimulate business and investment activities. Another, which some analysts say is especially true in the case of Japan, is to help exporters by depreciating its currency to make goods and services cheaper abroad. Atlanta Fed President Dennis Lockhart said on Thursday the BoJ's move to double its asset purchases - which will include exchange-traded funds and real estate investment trusts in addition to Japanese government debt - "if it works, will certainly help everyone." The BoJ is "doing what the Fed is doing in pushing people into risky assets," said Kristina Hooper, head of investment and client strategies at Allianz Global Investors in New York. It's too early to determine whether Bank of Japan's perceived gamble will ultimately pay off. The Nikkei stock index jumped 2.2 percent on the day, while the yen tumbled versus the dollar and the euro. Some analysts, however, were skeptical. "The odds of success are highly stacked against the experiment working," TD Securities interest rate strategist Richard Gilhooly wrote in a research note on Thursday. While investors mulled further over the longer-term impact of BoJ's stimulus burst, they will quickly turn their focus to Friday's U.S. payrolls report which could soothe some economic worries if it were to show another month of at least 200,000 jobs gained. A few analysts downwardly revised their forecast on March payrolls growth toward the 150,000 area after surprisingly weak March readings in the ADP private jobs report and job component in the Institute for Supply Management's services industry survey on Wednesday.