Mexico says it will rehabilitate five pumping stations in the border city of Tijuana to prevent cross-border sewage spills that have angered U.S. communities in the San Diego area.
The Foreign Relations Department said Wednesday the two countries "are in talks to sign a bilateral agreement that will establish commitments" on the issue.
A study by Mexican officials found polluted runoff likely comes from a Tijuana sewage treatment plant in need of upgrades that would likely cost upwards of $370 million.
Both countries "will commit resources to address the issue in a coordinated manner," the department said.
The move is the first step towards solving a long-standing problem that has become a source of contention between leaders on both sides of the border as to who is responsible for a solution.
The Tijuana River Estuary and shorelines from Imperial Beach to Coronado are often closed to the public after spills on the Mexican side of the border cross into the United States via the Tijuana River, especially following heavy rainfall.
Residents have reported skin rashes, headaches and respiratory issues, council officials said.
In 2018, local governments in the San Diego area sued a U.S. agency over the spills. The suit alleges millions of gallons of waste, including untreated sewage, trash, pesticides and heavy metals have been discharged from the IBWC's treatment facilities in violation of the Clean Water Act.
Imperial Beach, Chula Vista and the Port of San Diego sued the International Boundary and Water Commission's U.S. section for failing to prevent Tijuana sewage from flowing through the Tijuana River Valley to the Pacific Ocean, causing U.S. beach closures.
Regional leaders representing both the United States and Mexico met earlier this year to discuss ways to end the flow of raw sewage and pollution into the Tijuana River Estuary, though a solution was never presented.
San Diego Mayor Kevin Faulconer praised the move from Mexican leaders in a tweet Wednesday.
"We have forward movement from Mexico! This - along with additional resources from the US @EPA - begin the work to fix the TJ River Valley," he wrote.
The Tijuana River crosses the U.S.-Mexico border just west of the Otay Mesa Port of Entry and travels northwest, through the Tijuana River Estuary and into the Pacific Ocean south of Imperial Beach.