Copper fell on dollar strength on Thursday and after recent gains tempted investors to book profits, though sentiment remains underpinned by manufacturing reports from China and elsewhere that pointed to firmer demand. The dollar index hit a fresh seven week high as several U.S. Federal Reserve officials this week stoked the possibility of an interest rate hike later this month as the economy strengthens. A stronger-dollar makes dollar-priced commodities costlier for non-U.S. investors. Fed Chair Janet Yellen is set to speak on Friday, and could provide the strongest indication on a move in the coming weeks. China's factory activity expanded faster than expected in February, data showed Wednesday, as domestic and export demand picked up, adding to signs the global economy is gaining momentum even as fears grow of a surge in U.S.-led trade protectionism.