From January 12, 2009, all citizens of 27 countries covered by the visa waiver program of the United States will have to apply online for authorization to travel.

Singapore, Brunei, Japan, Australia and New Zealand are among the countries whose citizens can travel to the US without securing a visa.

The mandatory web-based system is known as the Electronic System for Travel Authorization. Visitors should apply at least 72 hours before takeoff.

The process is a shift from the current paper embarkation forms visitors fill out, to a web-based system under the US Department of Homeland Security.

The authorization is valid for multiple entries into the US for two years.