America’s nascent status as a net petroleum exporter is already at risk as plunging oil prices threaten domestic production and give a leg-up to world’s biggest producers. The U.S. only in recent months began exporting more petroleum than it imports, a shift fueled by record shale production in fields such as the Permian Basin. Now, amid the worst price rout in nearly three decades, American drillers are facing a million-barrel drop in production that could curb U.S. exports and set back the country’s march toward energy independence.

“The U.S.’s net exporter days may be numbered,” said Cailin Birch, a global economist at the Economist Intelligence Unit in London.

For four of the last six weeks, the U.S. has shipped out more crude and refined products than it’s brought in — but that margin is relatively thin. If shale output were to fall by 1 million barrels a day this year, as BloombergNEF estimates, that could be enough to take the U.S. from net exporter back to net importer.