Hoping to reassure markets in the wake of an angry breakdown in the federal budget negotiations, Congressional leaders raced Saturday to reach a new deficit-reduction agreement that Speaker John A. Boehner told colleagues could cut $3 trillion to $4 trillion in spending over 10 years. “We are working, and I’m confident there will be resolution,” Mr. Boehner told fellow House Republicans on an afternoon conference call, according to participants. “There has to be.” Mr. Boehner’s comments came a little more than a week before the federal government risks defaulting on its debts, a fate that could be avoided if Congress...