In the meantime, the debt ceiling impasse has driven up the yield on some very short-dated securities that are seen as most at risk of a delayed payment, fueling distortions in the bills curve. The most elevated rates are those around early June, close to the point that Treasury Secretary Janet Yellen has warned the US might run out of borrowing headroom. If the department can make it past mid-June, then it’s likely to get a bit of breathing room from expected tax payments and other measures, before facing fresh challenges from late July, where market pricing also indicates a degree of strain and concern.