The programme is part of a Biden administration effort to increase legal pathways to the US and discourage illegal border crossings but has been criticised by Republicans as overly permissive.

The programme allows up to 30,000 people into the US each month from Cuba, Haiti, Nicaragua and Venezuela if they have sponsors and meet other conditions. Sponsors must be in the US legally and have sufficient financial resources to support the person they are sponsoring for the duration of their stay.

The Department of Homeland Security said that it paused the issuance of travel authorisations under the programme “out of an abundance of caution” while it undertakes a review of supporter applications, a spokesman said in a statement.

A DHS official, speaking on condition of anonymity, said new approvals had been halted since mid-July to strengthen screening and vetting, but that the application portal has remained open.

The official said DHS pauses processing “fairly regularly” and expected the approvals to resume in the coming weeks.

On Friday, the Federation for American Immigration Reform, a group that favors lower levels of immigration, said it had obtained an internal review that found fraud in the programme, including fake Social Security numbers and many applications listing the same address.

A second DHS official said the draft report featured cases that merited further review and were not necessarily fraud.

DHS said that its screening of US-based supporters is separate from its vetting of programme participants and that it has “not identified issues of concern relating to the screening and vetting of beneficiaries.”

As of June 30, some 495,000 people from those nations had entered the US under the programme, which began for Venezuelans in 2022 and the others in 2023, according to DHS statistics.