The accord -- the result of more than 18 months of negotiations -- comes amid growing water scarcity on both sides of the Rio Grande river, which forms part of the shared border, the countries' boundary and water commission said.

The United States is consulting with Mexico about securing water deliveries as soon as possible during the current rainy season, the statement said.

"The last 30 years of managing over-stretched water resources in the Rio Grande basin have produced broad agreement that the status quo was not acceptable," said Maria-Elena Giner, US representative to the boundary and water commission.

Under a treaty dating back to 1944, Mexico supplies water to the United States from the Rio Grande in five-year cycles.

In return, the United States delivers water from the Colorado River.

The new agreement provides Mexico with "tools and flexibility" to provide water earlier in a five-year cycle to reduce or prevent shortfalls, the statement said.

The decades-old treaty has been the focus of diplomatic frictions in the past over delivery delays, as well as protests by Mexican farmers worried about the impact of drought on their crops.