By Damian Paletta and Carol E. Lee

Treasury Secretary Timothy Geithner told top lawmakers at a White House meeting Thursday that failing to raise the debt ceiling soon would have calamitous economic consequences and would be unconscionable, people familiar with the meeting said.

Treasury Secretary Timothy Geithner speaks on June 30 at a Clinton Global Initiative meeting in Chicago. (EPA/Tannen Maury)

Mr. Geithner’s comments came as the White House and lawmakers met to try and map out a way to reduce trillions of dollars from the deficit over the next decade, and much of the negotiating over the coming days is expected to be on the politics of getting a deal.

But Mr. Geithner, who could leave office soon after a deal is reached, told the small audience of Democrats and Republicans that the impact of failing to raise the debt ceiling would be stark, swift, and severe, the people familiar with his comments said.

The country owes far more money than it brings in each month because of obligations it has already made, and Treasury must borrow money to meet all of the government’s obligations. But it can only borrow money up to the limit set by Congress…