She warned that with interest rates already very low or even negative in many places, it would not be easy to respond if new difficulties emerged. In what appeared to be a veiled reference to possible economic consequences from a new virus in China and bush fires in Australia, Ms. Georgieva said that January had already produced events that posed new risks, and that policymakers would need to be able to respond more quickly than in the past when things went wrong.

Treasury Secretary Steven Mnuchin alluded indirectly to the new coronavirus that has led Beijing to quarantine more than a dozen cities in China this week, saying that health challenges need to be watched closely. Problems at Boeing — which has temporarily halted production of its 737 Max jets after two crashes — could trim American economic growth by as much as one-half to three-quarters of a percentage point in the short term, he said, while adding that the United States still has a “very robust economic outlook through 2020.”

Europe and Japan have been at the center of concerns that negative interest rates leave little room for policymakers to ease monetary policy and stimulate growth if needed. The top central bankers from both places acknowledged on Friday the dangers of negative interest rates even as they said they saw no immediate opportunity to tighten monetary policy.

Christine Lagarde, the president of the European Central Bank, said she welcomed figures showing lower unemployment in Europe and wages rising at a rate of 2.5 percent a year. But she warned that inflation had not yet risen to the point that the central bank could tighten monetary policy — which would push up short-term interest rates and leave room to cut them later.

“We are seeing inflation moving a teeny tiny bit,” she said.

Haruhiko Kuroda, the governor of the Bank of Japan, said the Japanese economy was likely to keep growing at its recent pace of 1 to 1.5 percent a year. While that has been enough to keep unemployment very low, inflation is also so low — well below 1 percent — that the central bank “will continue accommodative monetary policy for some time,” he said.