As reported by Lenta.ru, this rule was established by the US Department of Homeland Security. The head of the department, Michael Chertoff, is to make the corresponding official statement today, June 3.
Citizens of 27 countries, including most Western European countries, Australia, New Zealand, and Japan, may travel to the US without a visa for up to 90 days. In addition, it is expected that visa-waiver agreements will soon be reached with eight more countries, including the Czech Republic, Hungary, and South Korea, as well as the Baltic states.
Another requirement for those entering the US without a visa is having the required passport. If the document was issued after October 26, 2006, it must contain biometric data.