"I have authorized documentation to impose a 5% Tariff on Mexico if this water isn't released, IMMEDIATELY," Trump wrote on his Truth Social platform, saying crops and livestock were being badly affected in Texas.

Trump accused Mexico of violating a 1944 treaty under which the United States shares water from the Colorado River in exchange for flows from the Rio Grande, which forms part of the border between the two countries.

Trump said Mexico owed 800,000 acre-feet of water to the United States under the terms of the treaty, demanding it "release 200,000 acre-feet of water before December 31st, and the rest must come soon after."

"The longer Mexico takes to release the water, the more our Farmers are hurt," Trump added.

The move to boost water supplies for Texas farmers came the same day the 79-year-old president announced a $12 billion aid package for the US agriculture industry, rocked by fallout from his trade and tariff policies.

Trump in April had previously threatened Mexico with economic repercussions regarding the water dispute, prompting Mexico at the time to immediately send water and "continue fulfilling its commitments under the 1944 treaty."

Mexican goods currently face a 25% tariff unless they fall under the United States-Mexico-Canada Agreement (USMCA), a free trade deal struck during Trump's first term and which Washington is aiming to renegotiate in 2026.

Trump met with his Mexican counterpart Claudia Sheinbaum last week on the sidelines of the 2026 World Cup draw, along with Canadian Prime Minister Mark Carney, to discuss the future of the trade deal.

The talks marked the first in-person meeting between Trump and Sheinbaum.