How the US proposal will work
Airlines and cruise companies will need to collect the fingerprints of all foreign citizens leaving the United States.
The US government expects the companies to transmit the data to the Department of Homeland Security within 24 hours of their passengers' departure.
The proposal does not say where fingerprints must be collected - at airport check-in counters, departure gates or at kiosks somewhere in between.
Congress expects the Department of Homeland Security to finish collecting fingerprints from departing air passengers by June next year.
Failure to meet the deadline will mean the US government cannot expand the Visa Waiver Programme, under which residents of 27 friendly countries - including Singapore - can visit the US without a visa.
The proposal will open for a 60-day comment period.