The administration of United States President Donald Trump has announced a tougher policy against foreign nationals who travel to the country with the intention of giving birth and securing US citizenship for their children.

White House Deputy Chief of Staff for Policy and Homeland Security Adviser Stephen Miller said on Saturday that such travellers would no longer be allowed to obtain US visas for that purpose.

The administration considers “birth tourism” to be the practice of foreigners travelling to the United States specifically to give birth so their children can obtain citizenship by being born on American soil.

Miller said immigration officials would rely on existing US immigration laws to determine whether applicants were misrepresenting their reasons for travelling to the country.

The move is part of Trump’s wider effort to restrict birthright citizenship. His administration previously attempted to end the practice through an executive order, but the US Supreme Court later ruled against the policy.

Trump has criticised the court’s decision and said his administration would make adjustments to its approach.

The actual number of people involved in birth tourism remains uncertain. Trump has claimed that hundreds of thousands of people take advantage of the system, while US Solicitor General John Sauer acknowledged during Supreme Court proceedings that the government does not know the exact figure.

Miller also said the administration’s wider citizenship restrictions could affect certain categories of foreign nationals, including people linked to foreign governments and designated organisations.

Separately, Miller linked immigration to poor reading performance among some New York schoolchildren.

He cited figures claiming that a large proportion of children in New York were either foreign-born or children of migrants. However, he did not provide evidence establishing a direct connection between immigration and the reading difficulties highlighted in a recent report.