The Fed could also be more explicit in spelling out just how long it planned to keep rates at record-low levels. That would give investors confidence about the Fed's efforts to continue supporting the economy.

Mr. Bernanke maintained that temporary factors, such as high food and gas prices, have slowed the economy. He said they should ease in the second half of the year. But if that forecast proves to be wrong, he said the Fed is prepared to do more.

"The possibility remains that the recent economic weakness may prove more persistent than expected and that deflationary risks might reemerge, implying a need for additional policy support," Mr. Bernanke told the House Financial Services Committee on the first of two days of Capitol Hill testimony.

Mr. Bernanke also said it was possible that inflationary pressures spurred by higher energy and food prices may prove more persistent than the Fed is forecasting. He said that the central bank would be prepared to start raising interest rates faster than currently contemplated.

David Fuller's view QE3 is already widely anticipated, rightly or wrongly, although we can be certain that Mr Bernanke is desperately hoping that this will not be necessary. Unemployment is likely to remain stubbornly high, as I mentioned yesterday. With an election year coming up, the Fed will be under pressure to stimulate the economy, anyway it can.

A likely problem for Mr Bernanke is that commodity price inflation is not temporary in this era, due to increasing demand for all resources from growth economies, higher extraction costs and more turbulent weather than we had become accustomed to. Year-on-year measures of commodity inflation should disguise increases somewhat from 2Q 2012 onwards, given this year's earlier peaks in the Continuous Commodity Index, but households everywhere will certainly feel the pinch.