(Adds detail, quotes from second executive, byline) By Soyoung Kim NEW YORK, Sept 5 (Reuters) - Despite signs of steadier U.S.auto sales in August, it remains uncertain whether industrywidesales in the largest vehicle market have hit bottom, andconditions next year are unlikely to improve, senior ToyotaMotor Corp executives said on Friday. 'It's hard to say whether the U.S. market has hit bottom,'Toyota (7203.T: Quote, , Research, )(TM.N: Quote, , Research, ) Vice Chairman Kazuo Okamoto said at anevent hosted by the Japanese automaker for financial analystsin New York. Okamoto, speaking through a translator, also said thatdespite the recent decline in oil prices, Toyota was stillassuming oil prices would be higher over the long term, as thebasis for its product planning. The sharp decline in U.S. auto sales this year, prompted inpart by record gasoline prices, caught Toyota and other majorautomakers by surprise. Toyota, which has overtaken General Motors Corp (GM.N: Quote, , Research, ) asthe world's largest automaker and Ford Motor Co (F.N: Quote, , Research, ) as No. 2in the U.S. market, has seen its U.S. sales drop 8 percentthrough August. The overall market was down 11 percent through August. Coupled with a downturn in Western Europe, the ongoingdecline in the U.S. market forced Toyota to cut its forecastfor its worldwide 2009 vehicle sales late last month.