Homeland Security Secretary Michael Chertoff will announce the rule Tuesday, according to a government official who asked not to be identified because the announcement had not yet been made.
The rule was first reported by the Financial Times on Monday.
Required online registration will begin in January and will be valid for a two-year period.
Those needing to register will be travelers from the 27 countries whose citizens are not required to obtain visas for U.S. entry. The counties include those in most of western Europe as well as Andorra, Australia, Brunei, Japan, New Zealand and Singapore. Eight other countries -- the Czech Republic, Hungary and South Korea among them -- are expected to be admitted to the visa waiver program.
When the Homeland Security Department began discussing the online registration rule last year, European businesses worried that business travel could be impeded.