Jamie Dimon warned that a U.S. default would be “potentially catastrophic,” and pleaded with politicians to “please negotiate a deal” before the country breaches its borrowing cap in early June. If the U.S. defaults on its debt, the JPMorgan CEO warned in a Thursday interview with Bloomberg TV, it would hit “contracts, collateral, clearing houses, and affect clients definitely around the world.” Dimon expressed some hope that the U.S. would be able to negotiate a solution if markets begin to worry that a default might happen. "The closer you get to it, you will have panic" in terms of market...