ReutersOPEC Secretary-General Abdalla Salem al-Badri.OPEC’s top official said Sunday that the cartel’s decision to keep pumping crude in the face of collapsing prices is hurting the U.S. shale-oil industry and a global pullback on investment could lead to a shortage that will push the market upward again. “Projects are being canceled. Investments are being revised. Costs are being squeezed,” said Abdalla Salem el-Badri, the secretary general of the Organization of the Petroleum Exporting Countries, at the Middle East Oil and Gas conference in Bahrain. “If we don’t have more supply, there will be a shortage and the price will rise again.” Other top officials at the conference said they would maintain their response of continuing to pump in the face of collapsed prices caused in part by a glut of U.S. shale oil--a relatively new product obtained through hydraulic fracturing, or fracking, of shale rock formations underground. Brent crude, the global benchmark, was trading at about $60 a barrel on Friday, an amount that is almost half its price last July but that officials in places like Kuwait say they can live with. “We are very lucky oil prices did not drop to $20,” said Kuwait Oil Minister Ali al-Omair. Saudi Arabia’s oil minister Ali al-Naimi denied last week that OPEC nations were at war with U.S. shale producers, saying they welcomed them to the market. Mr. el-Badri echoed those remarks, but noted that U.S. shale was costly to produce. Saudi oil, by contrast, is cheaper to pull out of the ground. An expanded version of this report appears on WSJ.com.