The Federal Reserve kept its key interest rate unchanged at a low level Wednesday but cautioned that the world economy could be slowed by China’s coronavirus outbreak. The Fed presented a positive image of the U.S. economy in the statement it released after its last policy meeting. Chairman Jerome Powell said the Fed would continue to monitor the world economy amid the crisis, since stock and bond markets have been volatile in the past week over fears about the virus. China’s viral outbreak has effectively shut down much of the nation’s economy, which is the world’s second largest. Powell said that there were promising signs that the global economy would accelerate this year until the coronavirus outbreak. “It’s very uncertain about how far it will spread and what the (economic) effects will be in China, for its trading partners, and around the world,” the chairman said, adding that “there are signs and reasons to expect” a global economic rebound.