It's oil, not gas, that will increase U.S. leverage in the overseas market more quickly, the chairman of the largest stakeholder in North Dakota's oil said. The U.S. House Foreign Relations Committee heard testimony Wednesday on how best to exploit the glut of oil and natural gas brought on by the shale boom in the United States. With Russia aggravating Western leaders over its reaction to the Ukrainian crisis, U.S. policymakers say easing some of the restrictions on oil and gas exports could weaken the Kremlin's influence in Eastern Europe. Harold Hamm, chairman of Continental Resources Inc., the largest stakeholder in North Dakota oil fields, said the oil spigot would be easier to open. While Russia's primary "energy weapon" is gas, the United States lacks the infrastructure to have an immediate impact. "If we want to have an overnight impact on today's global events, we can immediately begin exporting crude oil, which does not have the same infrastructure constraints," he testified. Elizabeth Rosenberg, director of the energy and security program at the Center for a New American Security, said more exports could raise prices in the domestic market, though the trade off in terms of U.S. leverage made it "well worthwhile." Legislation enacted in response to the 1970s Arab oil embargo restricts U.S. crude oil exports. A special permit is needed to ship LNG to countries without a U.S. free-trade agreement, which no European country has currently.