President Donald Trump weighed in on a decades-old border water dispute on Monday, saying he would impose a 5 percent tariff hike on Mexican imports if the country fails to swiftly deliver the water it owes from the Rio Grande.

The ultimatum is designed to help struggling U.S. farmers, especially in Texas, amid alleged treaty violations over the past five years.

In a post on social media, Trump underscored an alleged 800,000 acre-feet debt from the recently ended cycle, demanding the release of 200,000 acre-feet before Dec. 31 and additional volumes shortly after.

The president highlighted the impact on Texas agriculture, where insufficient water undermines crop yields and livestock sustainability.

“As of now, Mexico is not responding, and it is very unfair to our U.S. Farmers who deserve this much needed water,” Trump said on Truth Social on Monday.

“That is why I have authorized documentation to impose a 5% Tariff on Mexico if this water isn’t released, IMMEDIATELY.”

As Kimberley Hayek reports for The Epoch Times, Mexico has in the past cited significant drought conditions curtailing its capacity.

The 1944 U.S.-Mexico Water Treaty regulates shared resources from the Rio Grande, Colorado, and Tijuana rivers.

For the Rio Grande segment south of Fort Quitman, Texas, the agreement states that the United States would receive one-third of flows from six Mexican tributaries—Conchos, San Diego, San Rodrigo, Escondido, Salado, and Las Vacas Arroyo—with a guaranteed minimum average of 350,000 acre-feet per year, or 1.75 million over each five-year cycle. The agreement allotted Mexico two-thirds of those flows, as well as allocations from U.S. tributaries, including the Pecos and Devils rivers.

In April, Trump criticized Mexico, threatening tariffs or sanctions if the country failed to adhere to the terms of the treaty.

“Mexico has been stealing the water from Texas farmers,” he posted at the time, pledging to “keep escalating consequences, including tariffs and, maybe even sanctions, until Mexico honors the Treaty, and gives Texas the water they are owed!”

Mexico’s President Claudia Sheinbaum highlighted the ongoing drought but vowed to help resolve the issue. Mexico said it would draw from its reserves and increase flows from the six tributaries through October, as announced by U.S. Agriculture Secretary Brooke Rollins. IBWC data, however, showed deliveries came in at approximately 730,000 acre-feet by mid-2025, 42 percent short of the 1.75 million obligation.

A history of lenient enforcement, hydrological changes, and rapid population increase in Mexico has been blamed for the current conditions.

Evan Ellis, a Latin American studies professor at the U.S. Army War College, said the current situation can be attributed to “years of looking the other way” by the United States.

The treaty allows for deferrals only during “extraordinary drought,” which is left undefined but requires repayment in the following cycle.

In March, the United States rejected Mexico’s request for Colorado River water diversions to Tijuana, noting Rio Grande shortfalls. It is the first time the country has denied such a request under the treaty.

The Texas agricultural sector depends on consistent water supplies, and the allocation shortfalls have led members of Congress to introduce bills proposing fund withholdings until remedies are secured.