Amazon purchased the Middle East’s biggest online retailer Souq.com on Tuesday for an undisclosed amount, a day after a state-backed firm disclosed an $800 million counteroffer. A joint statement described the purchase as expanding Amazon’s influence into the Mideast as the state-supported firm Emaar prepares to launch its own retail website in a country known more for its luxury malls than online shopping. That could put Seattle-based Amazon in a head-to-head competition with a firm helmed by one of the sheikhdom’s favored business magnates. “This is a milestone for the online shopping space in the region,” Souq.com co-founder and CEO Ronaldo Mouchawar said in a statement. The announcement said the two companies expect the sale to close this year. “Together, we’ll work hard to provide the best possible service for millions of customers in the Middle East,” Russ Grandinetti, a senior vice president at Amazon, …