The war in Iran has closed the Strait of Hormuz, leaving China's neighbors fuel-starved and increasingly dependent on Beijing. Countries across Asia are petitioning China for relief, handing Beijing the kind of regional sway it has long sought. Vietnam appealed for jet fuel, the Philippines asked for fertilizer, and Australia secured assurances of cooperation after its foreign minister visited China last month.

China is dealing from a position of strength. It has amassed huge oil reserves, reduced its dependence on foreign oil over decades, and poured hundreds of billions into clean energy technology. Shipments of jet fuel to Vietnam increased 34 percent, fertilizer exports to the Philippines rose 33 percent, and diesel exports to the Philippines surged 187 percent in March compared to the previous month.

China is positioning itself as a leader in renewable energy, in contrast to President Trump's embrace of fossil fuels that leaves much of the world exposed to Middle East volatility. "China is stepping in cautiously to support its neighbors," said Michal Meidan of the Oxford Institute for Energy Studies. "They are using this as a soft-power tool to lay the foundations for sales of green technology as a way of security in the future." Chinese solar panel exports more than doubled in March.