Mr. Geithner has been meeting privately with senior lawmakers of both parties to underscore the economic stakes. At the White House, Mr. Obama’s chief economic adviser, Gene Sperling, peeled away from the spending fight in recent weeks to turn nearly full time to developing the administration’s strategy for the debt-limit debate. Central to that, administration officials say, is whether Mr. Obama initiates bipartisan talks on a long-term debt-reduction plan that tackles taxes, military spending and fast-growing entitlement programs like Medicare and Medicaid…

“If anyone wants to push that button, which I think would be catastrophic and unpredictable, I think they’re crazy,” Mr. Dimon said recently at the United States Chamber of Commerce…

The just-concluded budget fight has spawned talk that the White House and Congress will perhaps resort to a series of short-term extensions of the debt limit while they bargain over a debt-reduction plan or some other mandatory budget restraints. The question is, how might global financial markets react?

“We’ve never seen that before,” said Robert E. Rubin, the Treasury secretary under President Bill Clinton and a longtime Wall Street executive. “But I know this: It’s not a risk I’d take.”