Eagle Pass, Texas - Former President Donald Trump and President Joe Biden paid rival visits to the US-Mexico border Thursday in a high-stakes battle for voters on one of the hottest issues in November's 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.

Republican Trump (77) touched down in Eagle Pass, Texas – and minutes later Democratic incumbent Biden (81) arrived in Brownsville, Texas about 300 miles to the east.

The split-screen moment eight months before Americans head to the polls in a tight election highlights how migration is set to be a make-or-break issue – especially for Biden.

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Making just his second border trip since taking office in 2021, Biden is meeting border patrol and other law enforcement agents, before giving a speech urging Republicans to stop blocking his immigration reforms.

Republicans had rejected Biden's proposed border legislation "simply because the former president [Trump] told them to," White House deputy press secretary Olivia Dalton told reporters on Air Force One.

Biden was accompanied by his immigration chief Alejandro Mayorkas, who was impeached by Republicans in the House of Representatives two weeks ago in a sign of how divisive the issue has become.

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 and sanctions imposed by the US.

Trump has pledged the biggest-ever US deportation program if he returns to the White House.

"Nice weather, beautiful day but a very dangerous border, we're going to take care of it," the frontrunner for the Republican presidential nomination told reporters as he landed in Eagle Pass.

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Trump's campaign described the border as a "crime scene" and said the former president would "outline his plan to put America first and secure the border immediately upon taking office."

The rival visits also underscored the candidates' radically different visions of the situation at the US-Mexican border.

Eagle Pass is a good fit for Trump, as Texas's Republican Governor Greg Abbott has taken military control of an area there along the Rio Grande that marks the border, sparking a standoff with the federal government.

By contrast, Biden's Brownsville trip aims to show how his border measures are working, in an area where so-called migrant "encounters" dipped by nearly a quarter in January.

Mayorkas said Biden would hear from border officials about the "too few resources they have," and how the legislation blocked by Republicans would give them the resources they need.

He also defended Biden avoiding an area where the crisis was worse, saying Brownsville showed how cooperation between the United States and Mexico had helped reduce border crossings.

"Brownsville provides a very good glimpse of how dynamic and challenging the migration phenomenon is," Mayorkas told reporters traveling with Biden.

Republicans blame Biden for the flow of migrants, while the White House says Trump's party is deliberately sabotaging a bipartisan attempt to find a solution.

But polls show the issue is a weakness for Biden's bid for a second term, with a survey from NBC in February showing Trump leading Biden by 30 points on the issue of immigration.

Biden insisted earlier this week that he hadn't deliberately planned the clash of schedules with Trump, the man he beat in the 2020 election, saying he didn't know his "good friend" was also going.