The emergence of Omicron raises the uncertainty around inflation, the chair of the Federal Reserve has warned.Rising rates of Covid, plus the new variant, pose new risks to the US economy, Jerome Powell told a Congressional committee.In the past Mr Powell has called recent high rates of inflation transitory, a term he said should now be "retired".He also said the Fed should consider tapering its bond-buying stimulus more quickly.During the course of the pandemic the Federal Reserve has been praised for warding off recession with its asset purchasing programme. This month it began the process of reducing that support, the first step towards increasing the cost of borrowing, the usual policy strategy to tame inflation.However a debate has arisen over whether the support should be withdrawn more rapidly.bbc.com