By insisting on fixed exchange rates, China and other emerging markets over the years have become a major exporter of capital "to such an extent that they have been significant drivers of lower global long-term interest rates," Mr. Carney told a full house of Vancouver business people.

Those sophisticated and poorly understood products are now the main conduit for contagion of the U.S. slowdown to the rest of the world.

Chinese economic policies "are not the sole factors, but they have contributed to the low level of monetary interest rates globally," Mr. Carney later told reporters.

"That has spilled over - both on the monetary policy side, because it has driven interest rates down."