Washington DC - President Donald Trump on Monday threatened to impose more tariffs on Mexico over what he claims are violations of a water-sharing treaty.

"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 US shares water from the Colorado River in exchange for flows from the Rio Grande, which forms part of the border between the two countries.

He claimed Mexico owed 800,000 acre-feet of water to the US 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 move to boost water supplies for Texas farmers came the same day Trump announced a $12 billion aid package for the US agriculture industry, rocked by fallout from his trade and tariff policies.

The 79-year-old had previously threatened Mexico with "consequences" over the water dispute in April.

Mexican goods currently face a 25% tariff unless they fall under the US-Mexico-Canada Agreement (USMCA), a free trade deal struck during Trump's first term and which he 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 agreement.