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.

“This is a big blow to those that were banking on the U.S. shale revolution,” said Ryan Fitzmaurice, commodities strategist at Rabobank. While oil demand may recover later in the year, shale will not be as quick to bounce back, he said.

The U.S. benchmark crude tumbled 25% on Monday to close at $31.13 a barrel, well below the average break-even price for producers in the three biggest U.S. shale fields. Major banks were quick to revise price forecasts downward as Saudi Arabia and Russia, the world’s two largest crude exporters, are poised to flood the market with discounted oil in an all-out price war.

The surge of inexpensive supply could pose a secondary blow to shale explorers, as U.S. refiners opt for foreign barrels over domestic.

“If there are additional medium sour volumes available and discounts to light sweet crude widen, I think some U.S. refiners will definitely look to import more crude,” said Chris Barber, principal at ESAI Energy.