US Treasury Secretary Henry Paulson has warned that the struggling US economy may face more rough times ahead but insisted that in the long run its prospects are strong and that Washington would work with its partners to take steps to avert future crises. "The financial market turmoil and its impact on global growth underscore the need for all countries to remain open to trade and investment," Paulson said after a meeting here of the Group of Seven major industrialized countries. "We have worked, and will continue to work, closely to address global challenges and take concrete actions," he said.