* FTSEurofirst 300 loses 1.1 pct, down 2.7 pct in August * Investors brace for flurry of U.S. macro data * Energy shares hit by sharp retreat in oil futures * For up-to-the-minute market news, click on [STXNEWS/EU] By Blaise Robinson PARIS, Aug 31 (Reuters) - European stocks were down around midday on Tuesday, on track to record their sixth monthly loss this year, as investors fretted about lingering worries over the health of the U.S. economy ahead of key macroeconomic data. At 1108 GMT, the FTSEurofirst 300 .FTEU3 index of top European shares was down 1.1 percent at 1,014.74 points in a broad retreat led by banking shares. Allied Irish Bank (ALBK.I) dropped 5.4 percent, Credit Agricole (CAGR.PA) fell 2.7 percent and BBVA (BBVA.MC) shed 2.1 percent. The Euro STOXX 50 .STOXX50E, was down 1.1 percent at 2,589.12, but off the day's low and back just above a key support level, the 23.6 percent retracement of a fall from an April high to a May low. The euro zone's blue chip index has lost 9 percent since Aug. 5, after a raft of grim economic data ignited fears the U.S. economy could slide into recession again. "Yesterday, the bulls failed to keep last week's rally going. We still think the indexes are heading for the year's lows," said Alexandre Le Drogoff, technical analyst at Aurel BGC, in Paris. On Tuesday, investors braced for a flurry of macroeconomic data, including the S&P Case/Shiller Home Price Index, the Institute for Supply Management's monthly index of business activity for the New York region, the Institute of Supply Management Chicago's monthly index of manufacturing activity, the Conference Board's consumer confidence data, as well as the Federal Open Market Committee's minutes from its meeting of Aug. 10. "We've have had a string of weak numbers, and now even second-tier economic data can have a big impact on the market," said Joost Van Leenders, investment specialist allocation and strategy at BNP Paribas Investment Partners in Amsterdam. "We're still 'underweight' equities because of the economic outlook. We've been expecting a slowdown in the second half of the year with the boom from inventories and stimulus spending fading, and it has actually been a bit worst than we had anticipated." Around Europe, UK's FTSE 100 index .FTSE was down 1 percent, Germany's DAX index .GDAXI down 0.8 percent, and France's CAC 40 .FCHI down 1 percent. A steep drop in oil prices CLc1 on expectations of higher crude inventories and worries about a weakness in oil demand hurt energy shares. The STOXX Europe 600 oil and gas index .SXEP fell 1.4 percent, with Royal Dutch Shell (RDSa.L) down 1.7 percent and BP (BP.L) down 1.6 percent. Shares in Dutch chip equipment maker ASML (ASML.AS) tumbled 4 percent to a nine-month low after brokers downgraded their ratings on the shares following Intel's (INTC.O) revenue warning last week. Among the few stocks on the upside, Italian telephone directory company Seat Pagine Gialle SpA (PGIT.MI) rose 2.6 percent, boosted by a report that PagesJaunes Groupe (PAJ.PA) was interested in buying the company. A PagesJaunes spokeswoman denied the report. (Reporting by Blaise Robinson; Editing by Mike Nesbit)

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