"Whether that is strong enough to put the whole world into recession or not, who knows, but it's bad," said Kohn, a former vice chairman of the Federal Reserve System.

"There are several dimensions in which I think this breaking, this beginning of fragmentation of the global trading system is very worrisome," he told a panel of British lawmakers.

(Reporting by David Milliken and Huw Jones, additional reporting by Estelle Shirbon, writing by Andy Bruce)