Japan's steel exporters could benefit from Prime Minister Shinzo Abe's aggressive economic reforms at the expense of U.S. competitors that specialize in the same high-end products. At the same time, the weaker yen resulting from "Abenomics" may benefit U.S.-based miners that supply steelmakers in Japan, which depend on iron ore and coal from abroad - especially if the government's massive asset purchases, infrastructure spending and other measures succeed in breaking Japan's nearly two-decade economic funk. U.S. steel imports from Japan jumped more than 30 percent in April from a year earlier, according to figures from the U.S. Census Bureau. That could be a one-month blip - preliminary data shows a 22 percent drop in shipments from Japan in May - but with all else equal, sustained weakness in the yen should boost Japan's exports, because it makes them cheaper. That has some in the U.S. steel industry worried. "I understand why they're doing what they're doing, (but) currency manipulation to help your exports is not supposed to be allowed," said Dan DiMicco, executive chairman of Nucor Corp told Reuters. DiMicco, an outspoken advocate for tougher U.S. trade policy, spoke on the sidelines of last week's Steel Success Strategies conference in New York, where the impact of Abenomics was a recurring topic of discussion. To be sure, Japan cannot begin to match the furious pace of exports from China, the world's top producer, where profit margins slid to 0.04 percent last year but local governments are keen to help mills survive and maintain employment, and a dramatic increase in Japanese exports could prompt anti-dumping measures in the United States. Still, China produces mostly basic grades of steel, while Japan's strength is in the high-end products, treated metal for automakers, for example, that are crucial to U.S. producers like United States Steel Corp. TRADE POLICY BACKLASH? Some U.S. steelmakers are already rallying behind a Senate bill that would require the U.S. Commerce Department to investigate whether currency manipulation is a form of trade subsidy, and potentially retaliate with duties on imports. Similar legislation failed to win congressional approval twice, in 2010 and 2011, even as some lawmakers accused China of deliberately undervaluing its currency to spur exports. A rise in the value of the yuan against the U.S. dollar has weakened that argument somewhat. But Thomas Gibson, chief executive of industry group American Iron and Steel Institute, said Japan's actions have strengthened the case for the bill. "The folks that reflexively defend China sometimes wanted to characterize it as penalizing China. It never was just focused on China, or penalizing China," he said. "It's a bill that has broader application." Kazuo Fujisawa, a general manager with major Japanese producer JFE Steel, a unit of JFE Holdings, takes issue with the charge of currency manipulation - quantitative easing is aimed at the scourge of deflation, he said. The yen, which was relatively strong until late last year, had put Japanese steelmakers at a disadvantage, he said, especially compared with South Korea, another major producer. SUPPLIERS COULD BENEFIT The problem, from Japan's perspective, is that higher rawmaterial costs may offset any gains in export revenue. Japan has no iron ore mines, and it is a major coal importer, and the weaker yen makes these imports more expensive. "If we are able to sell more on the international market that may be a plus. But at this moment we are more or less neutral," Fujisawa said. But Ernie Thrasher, chief executive of U.S. metallurgical coal exporter Xcoal Energy & Resources, said early signs don't point to that at all - Japanese companies are gaining more from the weak yen than they lose from higher raw material costs. Thrasher should know: Closely-held Xcoal markets metallurgical coal from U.S. mines owned by Consol Energy Inc and other companies. Some 73 percent of Xcoal's b