Regulators from the United States and the United Kingdom will get together in a war room next week to see if they can cope with any possible fall-out when the next big bank topples over, the two countries said on Friday. Treasury Secretary Jack Lew and the UK’s Chancellor of the Exchequer, George Osborne, on Monday will run the first-ever joint exercise simulating how they would prop up a large bank operating in both countries that has landed in trouble.