The U.S. economy has weathered the blow from recent devastating hurricanes and still has good momentum, Federal Reserve Chairman Alan Greenspan said on Thursday, though inflation risks are a worry, Reuters reported. "The economic fundamentals remain firm, and the U.S. economy appears to retain important forward momentum," Greenspan told the congressional Joint Economic Committee. "Structural productivity continues to grow at a firm pace, and rebuilding activity following the hurricanes should boost real GDP growth for a while," he said. "More uncertainty, however, surrounds the outlook for inflation." The 79-year-old Fed chief, who steps down at the end of January, also warned the United States must take steps to boost its supplies of natural gas, though he said they seemed adequate for the moment. "However, a colder-than-average winter would stress this market, and prices will likely remain vulnerable to spikes until the spring," he said. In response to questions, he warned U.S. consumers might be "quite surprised" by the heating bills they receive this winter. --More 2320 Local Time 2020 GMT