"While some improvement in labour markets has been achieved, it does not yet constitute progress sufficient to merit halting the asset purchase program," Rosengren told the Economic Club of Minnesota in Minneapolis.
He said he expects the unemployment rate will be down to 7.25 per cent "or a bit lower" by the end of the year.
"I believe the Fed should continue the purchase program until we see more sustained improvement in labour markets and have greater confidence that the economic recovery is sufficiently self-sustaining to yield continued progress in reducing the still very high unemployment rate," the Fed official said.
Indeed, the International Monetary Fund downgraded its growth forecast for China, the world's second-largest economy. China's economy will grow 7.75 per cent this year and next, the IMF said. That's down from an April forecast of 8 per cent for 2013 and 8.2 per cent in 2014.
And in Germany unemployment increased more than expected. The number of jobless Germans rose 21,000 in May, compared with expectations for an increase of 5,000 in polls by Reuters and Bloomberg.
Europe's benchmark Stoxx 600 Index sank 1.9 per cent. Elsewhere, Germany's DAX fell 1.7 per cent, while France's CAC 40 lost 1.9 per cent and the UK's FTSE 100 weakened 2 per cent.