Seven countries have joined a U.S. program for visa free travel.

The United States said that Hungary, Latvia, Lithuania, Estonia, the Czech Republic, Slovakia and South Korea were added to the U.S. visa waiver program Monday. President George W. Bush announced the expansion of the program last month.

The countries had to meet several requirements, such as issuing hard-to-forge passports and upgrading anti-terrorist laws.

Participants using the program will have to register online before traveling.

The countries join 27 nations in the program.