More poor economic data have put Washington in a nearly impossible fiscal position. The US economy requires more stimulus than provided by the original package passed in March. But the dismal deficit outlook poses a huge longer-term threat. Indeed, it is just a matter of time before global financial markets reject this fiscal trajectory.

That could lead to a punishing dollar crisis. To avoid it, America’s leaders should commit now and in detail to implement deficit reduction once the economy has strengthened. Vague promises will not work.