Oil prices approached 68 usd a barrel in Asian trade as a tropical storm threatened production platforms and refineries in the US Gulf Coast, dealers said. Lower-than-expected gasoline inventory levels in the US heightened concerns over supplies and helped push prices higher, they said, adding it may only be a matter of time before prices reached 70 dollars. At 10.25 am (0225 GMT), New York's main contract, light sweet crude for delivery in October, was trading at 67.71 usd a barrel, up 39 cents from its close of 67.32 usd in the US overnight. Oil futures prices had touched an all-time high of 68 usd a barrel in after-hours electronic trading. "The market is reacting to the tropical storm in the Gulf of Mexico which could affect platforms and refineries," said Victor Shum, a partner with US energy consultancy Purvin and Gertz in Singapore. "Coupled with the weather news is the inventory report showing a continuing gasoline drawdown which was larger than expected. It's now seven weeks in a row for gasoline so the two major news (items) really caused concerns in the market this morning." Shum said oil at 70 usd a barrel would not be surprising. "I think heading to 70 usd at some point would not be surprising. I think the market sentiment is that at some point it will hit 70. It's a matter of time," he said. The US Gulf Coast is gearing up for tropical storm Katrina, which was expected to intensify after sweeping past the Bahamas, the US National Hurricane Center said. Katrina is the 11th storm of the June-November Atlantic hurricane season. Separately, the US Department of Energy said crude oil supplies increased 1.8 mln barrels in the week to August 19 -- well above market predictions of a 200,000-barrel rise. But gasoline reserves dropped sharply by 3.2 mln barrels, after a fall of 5 mln barrels the previous week. The figure beat analysts' forecasts of a 900,00-barrel