President Joe Biden and Donald Trump have made competing visits to the US border in Texas, each seeking to stress they can tackle illegal immigration.
The issue is one of the most polarising in US politics, and will be central to this year's presidential election.
November's contest looks likely to be another showdown between the two men.
Mr Biden accused his Republican rival - who spoke of the "very dangerous" situation at the border - of hindering his efforts to crackdown on crossings.
Republicans in the House of Representatives have blocked bipartisan border reforms, in what Democrats say is an effort masterminded by Mr Trump to deny them a win before the election.
In Texas, Mr Trump said he would "take care" of the issue of illegal immigration if he was re-elected. He has previously promised mass deportations if he wins power again.
The issue is an intense focus because more than 6.3 million migrants have been detained crossing into the US illegally during Mr Biden's tenure - a higher number than under previous presidencies.
However, experts say the reasons for the spike are complex - with some factors pre-dating his government and sitting outside American control.
For more updates: www.globallupdates.com
