The arbitrage window for American crude shipments to Asia could soon close amid surging tanker rates and cheaper Middle Eastern oil which is also closer to the world’s top demand region than the U.S. Gulf Coast. The rates for chartering a supertanker, the so-called very large crude carrier (VLCC) capable of transporting up to 2 million barrels of oil, from the U.S. Gulf Coast to Asia has jumped to $70,000 per day in recent weeks, according to data from the Baltic Exchange cited by Bloomberg. The rates for supertankers on the Middle…