Federal Reserve Chair Jerome Powell warned Wednesday that the viral epidemic is endangering the modest economic recovery that followed a collapse in hiring and spending this spring. As a result, he said, the Fed plans to keep interest rates pinned near zero well into the future. That faltering economy, pressured by a resurgence of the virus, has heightened the need for Congress to continue providing significant financial aid, Powell said. Members of the House and Senate are negotiating a new package but are nowhere near agreement. Senate Republicans and the White House are proposing a plan that would provide less help for unemployed Americans than they are now receiving. Speaking at a virtual news conference after a two-day Fed meeting ended, Powell said the economy had rebounded after nearly all states lifted their broad business shutdown measures in May. But since then, he noted, as new confirmed cases have soared, measures of spending and hiring have slipped or plateaued at low levels.