"We are pressing to build preclearance capability at foreign airports around the world that have flights directly to the United States. Preclearance means screening by our customs personnel at the front end of the flight, not the back end. This provides us with a greater ability to prevent those who should not be flying here from doing so. Preclearance exists at 15 overseas airports now, and we are building more. In May I announced 10 overseas airports we have prioritized for preclearance

"At present there are 38 countries from which someone may travel to the United States without a visa.