* Crude futures settle lower * Brent premium to U.S. crude increases NEW YORK, Aug 6 (Reuters) - Most cash crude differentials inthe United States strengthened on Tuesday as the transatlanticspread between Brent and U.S. crude futures widened while crudefutures pushed lower, traders and brokers said. Brent crude's premium to U.S. crude futures ,also known by the benchmark crude grade, West Texas Intermediate(WTI), ended at $2.88 a barrel based on September contractsettlements after closing at $2.14 on Monday. The spread onMonday ranged from $1.82 to $2.94. Brent's premium reached $4.01 intraday on July 30, thehighest since U.S. crude was at a premium intraday on both July19 and July 22. Usually, the wider the arbitrage, the more supportive it isfor U.S. cash crude differentials, while a narrower spread oftenpressures differentials. This holds especially true for sweetgrades, which are priced in line with global waterborne crudessuch as Brent. Crude futures fell on Tuesday after Iran's new presidentsignaled his willingness to negotiate with the West on Tehran'scontroversial nuclear program and as U.S. gasoline futures werepressured after a selloff in ethanol credits. CASH CRUDE TRADES Light Louisiana sweet crude oil for September tradedfrom $5.25 to $5.60 over the September U.S. light sweet crudefutures contract. Heavy Louisiana sweet traded at $4.80 and $5.00 overthe futures benchmark, stronger after Monday's trade $4.70 overthe benchmark. Mars sour crude, a Gulf of Mexico-produced grade, hadSeptember barrels traded at 40 and 55 cents over the futuresbenchmark, stronger than Monday trades at 10 cents over thebenchmark. A trade for October barrels was seen at $1.10 under thefutures benchmark. Bonito sour traded on Tuesday at $3.00 over thefutures benchmark, after trading on Monday at $2.80 over thefutures benchmark. Eugene Island crude, another Gulf of Mexico producedcrude, traded at $2.90 and $3.00 over the futures benchmark,stronger after Monday's trades at $2.75 and $2.80 over thebenchmark. A September cargo of Alaska North Slope traded on Tuesday at$3.95 a barrel over the benchmark, weaker after the most recenttrades in late July completed at $4.40 over. MIDLAND GRADES West Texas Intermediate crude at Midland forSeptember traded at 35 cents under the benchmark futures,keeping the differential steady to trades on Monday. West Texas Sour crude, also at Midland, traded at 10cents under the futures benchmark, also steady to Monday'strades. CRUDE FUTURES Brent September crude fell 52 cents to settle at$108.18 a barrel, having traded from $107.46 to $109.23. U.S.September crude fell $1.26 to settle at $105.30 a barrel,having traded from $104.86 to $107.27. (Reporting by Robert Gibbons, editing by G Crosse)
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