The stronger dollar is acting as a headwind for the U.S. economy, and the global slowdown remains a risk, said White House chief economist Jason Furman on Tuesday.In a speech at the National Association of Business Economics, Furman was not pessimistic, saying that the depressing impact of the stronger greenback has so far been roughly offset by lower oil prices.“The U.S. economy has seen increased domestic momentum,” Furman said, adding that 87% of the U.S. economy is not affected by the trade sector.But he said the administration would remain vigilant about the global slowdown, not only because of trade but also because of the global financial system and overseas earnings.Furman repeated that the administration is opposed to addressing currency manipulation in a Pacific-Rimtrade deal.