Over the next six weeks, negotiators must strike a bipartisan compromise to slice more than $2 trillion from the federal budget by 2021, reduce the complex plan to writing and persuade a bitterly divided Congress to support it.

But one or both chambers is due to be on break for three of those weeks. And when Congress last reached a big debt-reduction deal, it took more than a month just to draft the legislation. That leaves little room for chance — or last-minute negotiating to marshal votes for what is likely to be a politically difficult package of unprecedented cuts to long-sacrosanct federal programs…

With an Aug. 2 deadline nearing, along with the threat of turmoil in global financial markets if Congress doesn’t act, Vice President Biden is stepping up talks this week with six lawmakers from both parties in hopes of presenting a plan to President Obama and congressional leaders by July 4. So far, negotiators have identified many areas of consensus: Farmers are certain to lose some federal subsidies, for example. And federal workers will have to contribute more to finance their retirement.

But what Biden called “the philosophically big-ticket items” remain: the Republican demand for significant savings from Medicare, the biggest driver of future deficits, and the Democratic demand for fresh revenue.