The US says it will tighten travel restrictions on foreigners who visit the country without needing full visas.
About 20 million people from 38 countries enter America each year under the visa waiver programme.
It has come under increased scrutiny since last month's attacks in Paris, with lawmakers expressing concern that militants could get into the US.
Under changes that are be submitted to Congress, all countries in the scheme would be asked to issue "e-passports".
Their registrations would come under greater scrutiny from US agencies, and travellers would also be screened to see if they had travelled to militant-held areas.