President Joe Biden and Donald Trump will pay dueling visits to the US-Mexico border Thursday to try to win over voters on a potentially decisive issue in November's presidential election.
The Texas showdown comes at a time when record numbers of migrant crossings into the United States are posing a threat to Biden's chances of preventing a Trump comeback.
Democrat Biden will meet border patrol and other law enforcement agents in Brownsville, Texas -- while Republican former president Trump heads to Eagle Pass, about 300 miles (480 kilometers) to the west.
Biden, 81, has sought to defuse the politically toxic border issue by blaming Republicans in Congress for sabotaging an immigration reform package negotiated over months by both parties.
On just his second trip to the border since taking office in 2021, White House Press Secretary Karine Jean-Pierre said Biden would deliver remarks in Brownsville to show how Republicans had "gotten in the way" of a solution.
But polls show the issue is a weakness for Biden's bid for a second term, with Republicans blaming the flow of migrants on his policies favoring the right to asylum.
- 'Crime scene' -
More than 2.4 million migrants crossed the southern US border in 2023 alone, largely from Central America and Venezuela as they flee poverty, violence and disasters exacerbated by climate change.
For Trump, 77, a hardline anti-immigration stance has been central to his political identity for years, and he has pledged the biggest ever US deportation program if he returns to the White House.
Trump's campaign described the border as a "crime scene."
"He will outline his plan to put America first and secure the border immediately upon taking office," during his visit, campaign press secretary Karoline Leavitt said in a statement.
The split-screen moment less than eight months before Americans go to the polls will highlight the candidates' radically different visions of the situation at the US-Mexican border.
Biden's trip to Brownsville will be aimed at showing how his border measures are working, in an area where so-called migrant "encounters" dipped by nearly a quarter in January.
By contrast Trump is traveling to a town where Texas's Republican Governor Greg Abbott has taken military control of an area along the Rio Grande river that marks the border, sparking a standoff with the federal government.
Populist Trump has also stepped up his rhetoric against migrants, saying at a Conservative event at the weekend that they were "killing our people, they're killing our country."
- 'My good friend' -
Biden insisted earlier this week that he hadn't deliberately planned the clash of schedules with bitter rival Trump, whose rhetoric the Democrat has likened to that of the Nazis.
"I planned for Thursday. What I didn't know was that my good friend apparently is going," he told reporters.
Biden also declined to say whether he would meet with migrants, after criticism that he did not do so on a previous visit.
Republicans blame Biden for the flow of migrants, while the White House says that Trump's party is deliberately sabotaging a bipartisan attempt to find a solution.
The border issue has also become tangled up in a row over US aid for Ukraine's fight against the Russian invasion, with Republicans insisting migration must be tackled before they unblock funding for Kyiv.
Public concern about illegal immigration is higher under Biden than it was under the last two administrations, with a majority now supporting a border wall of the kind Trump started building, according to a new poll by Monmouth.
A poll by US broadcaster NBC in February showed Trump leading Biden by 30 points on the issue of immigration.