For decades, the United States has relied almost exclusively on grants to deliver foreign assistance. While grant-based assistance remains essential in the poorest countries and for meeting health and humanitarian needs, grants are poorly suited to financing large-scale infrastructure, where funding needs far exceed grant budgets, and may be less attractive to middle-income countries seeking larger volumes of finance at below-market rates. Amid growing budget pressures, the United States needs a broader toolkit for engagement, and concessional loans could help fill a key gap at a fraction of the cost.