The Globe and Mail reports in its Friday edition that the United States could be heading for a debt crisis as soon as 2028, according to a warning from BofA Securities rates and currencies strategist Meghan Swiber. The Globe's Scott Barlow writes that in a report to clients, Ms. Swiber emphasized that the interest expense on U.S. federal debt -- which recently crossed the $40-trillion (U.S.) threshold -- is compounding quickly as borrowing costs climb. The strategist estimates that current government borrowing costs are about 100 basis points or one percentage point above the Congressional Budget Office's baseline expectations. The higher rate would add $4-trillion (U.S.) to interest costs in the next decade. Debt crises occur when the interest expense grows faster than nominal gross domestic product. More bond issuance is required to make interest payments and this borrowing adds to interest costs, requiring more issuance, and the debt spiral accelerates. This is not a problem yet; U.S. growth remains strong. But as higher borrowing costs slow GDP growth, Ms. Swiber's warnings become more salient.