The US is reviewing the records of more than 55 million US visa holders to assess if they have broken conditions for entry or stay in the country.

People with US visas will be under "continuous vetting", a state department spokesperson told the Associated Press news agency.

Visas will be revoked if there are indications of "overstays, criminal activity, threats to public safety, engaging in any form of terrorist activity, or providing support to a terrorist organisation", an official said.