This month's vote on the U.K.'s membership in the European Union will overshadow other risks and could spur the U.S. Federal Reserve to delay an interest rate hike, Axel Weber, chairman of UBS and a former central banker, told CNBC.
With the referendum on whether the U.K. should "Brexit" too close to call, "it creates huge uncertainty," Weber, who was president of the German Bundesbank from 2004-2011, told CNBC's "Street Signs" in an exclusive interview.
"You already see that British assets have a risk premium attached to them over recent months, including the pound," he said.
From a peak of around $1.5882 in mid-June of 2015, the pound is now fetching around $1.4431, losing more than 9 percent of its value against the greenback.
Concerns about the referendum may factor in to the Fed's decision-making on a rate hike, which has been clearly signaled as likely in June or July.
"I think June, because of the British poll, is less likely to some degree than a July move," Weber said.