As many as 20 million people around the world currently face starvation or the risk of it, because of the first United Nations-declared famine since 2011 – in South Sudan – plus the prospect for other famines later this year in northern Nigeria, Somalia and Yemen.

This preventable tragedy challenges the United States to act according to its proudest humanitarian traditions, not the selfish slogan of “America First.” And it’s an occasion to reconsider the government’s longstanding approach to international food aid, which caters to domestic special-interest groups at the expense of hungry people abroad and taxpayers at home.

Title II of the Food for Peace Act, the main source of emergency food aid, requires the United States to supply international famine-relief programs with American-grown products and to ship at least half of the materiel on U.S.-flagged vessels.

Meanwhile, at least 15 percent of the goods must be “monetized” once they arrive at their destination – that is, resold on local markets by nongovernmental organizations, to fund development projects. Obviously, this is good for American farmers, food processors, maritime unions, ship-owning companies and ports. Equally obviously, it makes the program less efficient than it might be: The set-aside for U.S.-flagged vessels inflates transportation costs; the buy-American rule for commodities prevents purchases from cheaper producers closer to the famine zones, whose productive efforts are also undercut by “monetization.”

Food-aid reform has been a bipartisan cause backed by each of the past two presidents and many members of Congress. However, the powerful lobbies that benefit from the status quo have prevented it. If he’s really interested in improving the cost-effectiveness of aid, President Trump would spend some of his political capital on the cause. Of course, that would also require him to depart from the simplistic “buy American” mind-set he has repeatedly expressed.