US Federal Reserve chairman Mr Alan Greenspan says the strength of the current US economic recovery is not yet clear and warns a lasting rise in energy prices could have "far-reaching" consequences.
The Fed chief praised the economy's resilience in the face of some difficulties. "But the strength of the economic expansion that is underway remains to be clarified," Mr Greenspan said in testimony prepared for delivery to the congressional joint economic committee.
However, the central bank chairman said there were encouraging signs of an increase in US final demand - seen as crucial to the recovery by Fed officials -- while adding that the dimension of the pickup remained uncertain.
The Fed chief's overall cautious tone is likely to bolster a growing view among economists that interest rate increases are not imminent.