The head of US bank JPMorgan Chase has said the bank is not planning to move many jobs out of Britain in the next two years in a softening of tone on the likely impact from Brexit. 

Jamie Dimon had said in a previous speech to employees in Bournemouth last year that as many as 4,000 of the bank's 16,000 jobs based in Britain may have to move. 

Even though his stance appears to have moderated Dimon said the bank is preparing for a so-called "hard Brexit" in which Britain loses access to EU's single market, disrupting access to its main trading partner.

"This does not entail moving many people in the next two years," he said in a letter to the US bank's shareholders.

Dimon also said the likelihood that the EU could break up has increased, which he warned could have a "devastating" economic and political impact.

He said that he hoped that Britain's decision to leave the EU would have force the bloc to focus on "fixing its issues," such as immigration, bureaucracy and rigid labour rules.

"Our fear, however, is that it could instead result in political unrest that would force the EU to split apart," he said. 

"We will keep a close eye on the situation in Europe over the next several years," he added.