The high rates of productivity growth that have helped boost the US economy's performance and hold down inflation show few signs of tapering off, Federal Reserve chairman Alan Greenspan said yesterday.

Giving an optimistic view of the immediate future of US productivity growth, Greenspan told a top-level meeting of central bankers and economists that the latest technological developments had helped raise the rate of productivity growth.

But that pace of growth - US productivity outside the farm sector grew at a 5.3 per cent rate in the second quarter from a year ago - will inevitably slow "at some point in the future," he cautioned. Mr Greenspan said even when the "virtuous cycle" of strong growth and low inflation that have fuelled the longest-ever US economic expansion starts to fade, the more efficient ways of doing business achieved through technology will stay.

The outlook for technology-driven productivity growth rates has grabbed centre stage in the debate about the future of US short-term interest rates, which are now at their highest level in almost a decade.