(FILES) In this file photo US Federal Reserve Chairman Jerome Powell gives a press briefing after the surprise announcement the FED will cut interest rates on March 3, 2020 in Washington,DC. /AFP

The recent efforts to distribute a Covid-19 vaccine offer hope to the economy, but the outlook remains "extraordinarily uncertain," Federal Reserve Chair Jerome Powell said Wednesday.

"Recent news on vaccines has been very positive," Powell told reporters after a two-day policy meeting in which central bankers saw a slightly improved growth and jobs outlook.

However, "significant challenges and uncertainties remain" on how quickly the vaccine can be pushed out to populations.