WASHINGTON (Reuters) - President Donald Trump’s nominee to be U.S. Trade Representative said on Tuesday that he believes China substantially manipulated its currency in the past to gain a trade advantage, but it was unclear if Beijing is still doing so. “In the past, it is my judgment that China was a substantial currency manipulator and I think we’ve lost a lot of jobs in the United States because of it,” Robert Lighthizer told senators in his confirmation hearing. “Whether China is manipulating its currency right now, to weaken it, that’s another question,” Lighthizer said, adding that U.S. Treasury Secretary Steven Mnuchin would be the person to make that determination. Trump pledged during his campaign that he declare China a currency manipulator on the first day of his administration, a move that would trigger demands for bilateral negotiations over this issue. He has not done so. China in the past year has spent hundreds of billions of dollars in foreign exchange reserves to prop up the value of its yuan in the face of capital outflow pressures.      