Mexican President Claudia Sheinbaum said Tuesday her country intends to send more water to the United States but cannot meet President Donald Trump's demand for an immediate release, citing physical constraints on how quickly water can flow through existing pipelines.

Sheinbaum's response came hours after Trump threatened to impose an additional 5% tariff on all Mexican imports if Mexico does not immediately deliver water it owes under a decades-old sharing agreement. The dispute centers on Rio Grande water that Texas farmers depend on for irrigation.

"We have the best intention to deliver the amount of water that is owed from previous years," Sheinbaum said during her morning press conference. She added that Mexico is proposing a water delivery this month and another in the coming years.

Mexican and US officials were scheduled to meet virtually Tuesday to discuss the proposal.

Trump's demand and tariff threat

Trump posted on social media Monday that Mexico's failure to comply with the 1944 Water Treaty is "seriously hurting our BEAUTIFUL TEXAS CROPS AND LIVESTOCK." He said Mexico owes the United States more than 800,000 acre-feet of water accumulated over the past five years.

An acre-foot is the volume of water needed to cover one acre of land to a depth of one foot—roughly enough to fill half an Olympic-size swimming pool.

"The U.S needs Mexico to release 200,000 acre-feet of water before December 31st, and the rest must come soon after," Trump wrote. "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 he has "authorized documentation to impose a 5% Tariff on Mexico if this water isn't released, IMMEDIATELY."

"The longer Mexico takes to release the water, the more our Farmers are hurt," he added. "Mexico has an obligation to FIX THIS NOW."

This marks the second time this year Trump has threatened tariffs over the water dispute. In April, he made similar threats before the two countries reached an agreement under which Mexico committed to send water from international reservoirs and increase US flow from six of Mexico's Rio Grande tributaries.

Physical constraints

Sheinbaum said Mexico cannot comply with Trump's timeline regardless of intent. The size of the pipeline carrying water to the Rio Grande creates a physical limitation on how much water can be delivered in a short period.

"Due to the size of the pipe, it would not be possible to deliver the amount of water requested in a very short time," Sheinbaum said.

She also noted that Mexico is constrained by its own water needs under the treaty. The 1944 agreement requires Mexico to deliver 1.75 million acre-feet of water from six tributaries to the United States every five years, averaging 350,000 acre-feet annually. In exchange, the US must deliver 1.5 million acre-feet to Mexico from the Colorado River each year.

Mexico has fallen behind on its obligations due to drought conditions and the pipeline limitations Sheinbaum cited.

The Texas Commission on Environmental Quality has tracked Mexico's shortfall. According to the agency, Mexico ended the latest five-year cycle with a debt of 925,000 acre-feet of water.

"TCEQ continues to work closely with our federal partners, including the International Boundary and Water Commission (IBWC) to have reliability and consistency under the treaty," the agency said in a statement.

Drought and climate concerns

Mexico's water commission, CONAGUA, has maintained that the country is not unwilling to comply with treaty obligations but is simply unable to do so under current conditions.

"We want to comply with the treaty—from which both countries benefit greatly. But we are in a drought situation made worse in recent years due to factors such as climate change," a Mexican official told Border Report earlier this year.

The two countries have clashed over the treaty before, but the current drought-driven shortages are the most severe in nearly 30 years. Texas farm groups warned last year of a disastrous season for citrus and sugar crops as officials from both countries worked to address the dispute.

Those shortages have killed crops and jobs and threatened the economy of the Rio Grande Valley, where farmers and ranchers depend on treaty water for their operations.

History of the dispute

The 1944 Water Treaty established a framework for sharing water resources between the United States and Mexico through a network of dams and reservoirs along the Rio Grande and Colorado River.

Under the agreement, Mexico's delivery obligations are measured in five-year cycles. When Mexico falls short in one period, the debt carries forward, creating cumulative shortfalls that can become significant during extended droughts.

The April agreement between the Trump administration and Mexican officials was meant to address the growing deficit. US Secretary of Agriculture Brooke Rollins called that deal a significant step forward and said the administration welcomed Mexico's continued cooperation in support of American agriculture.

But the shortfall has persisted, prompting Trump's renewed threats.

Sheinbaum expressed hope Tuesday that the two countries would again find common ground, as they have in past disputes over water sharing.

"I expect to reach an agreement with the United States," she said.

The outcome of Tuesday's virtual meeting between Mexican and US officials was not immediately known. If no agreement is reached and Trump follows through on his tariff threat, the 5% increase would add to existing duties already in place on Mexican goods, raising costs for American importers and potentially consumers.

Mexico is one of the United States' largest trading partners. Any additional tariffs would affect a broad range of goods flowing across the border, from automobiles and auto parts to agricultural products and manufactured goods.

For now, Texas farmers remain caught between two governments negotiating over water that treaties promised them decades ago but that nature and infrastructure have made increasingly difficult to deliver.