WASHINGTON -- Travelers from Japan and Western Europe will face tighter restrictions on coming to the United States beginning in January, according to new rules unveiled Tuesday by the US government.

Tourists and business travelers from the 27 countries currently listed under the visa waiver program will have to register with the US government three days in advance, the Department of Homeland Security said.

The new rules aim to make it more difficult for potential terrorists to enter the United States from places such as France, Germany, Switzerland, Britain, Belgium, Portugal, Spain, Singapore, New Zealand, Japan and Australia, the government said.

However, critics have raised concerns about the possibility of reduced tourism and difficulties with last-minute business travel.

"Getting this information in advance enables our frontline personnel to determine whether a visa-free traveler presents a threat, before boarding an aircraft or arriving on our shores," said Homeland Security Secretary Michael Chertoff.

"It is a relatively simple and effective way to strengthen our security, and that of international travelers, while helping to preserve an important program for key allies."

The government will ask for the same information that travelers currently fill out on the I-94 card which is handed out on the plane and turned in to customs on arrival in the United States, a DHS official told AFP.

That includes such information as passport number, country of residence, disclosure of communicable diseases or involvement in terror activities.

Travelers may register with the US government beginning in August, and the information will remain valid for a maximum of two years so it is not necessary to repeat the same process in that time period.

Once the regulations become mandatory in January 2009, all US-bound travelers from the countries affected "will need to receive an electronic travel authorization prior to boarding a US-bound airplane or cruise ship," it said.

Under the new program, known as the Electronic System for Travel Authorization (ESTA), travelers will have to apply for authorization on the Internet at a US government website, or through their travel agent.

EU Justice Commissioner Jacques Barrot wants to establish whether the system would amount to a de-facto visa, and has asked Chertoff by phone for "more information in detail and for documents so they could be studied," a spokesman said in Brussels.

"We have to see what data the Americans are going to ask for, how they plan to manage and use them."

The website, https://esta.cbp.dhs.gov/, will accept applications beginning August 1 and "will employ technology to prevent unauthorized access to the information entered and viewed."

"Access to such information is limited to those with a professional need to know," the DHS said on its website.

If a traveler is denied ESTA authorization, the alternative is to apply for a nonimmigrant visa at a US embassy or consulate, and accommodations will be made for last-minute and emergency travel, DHS said.

ESTA was called for under the "implementing recommendations" of the 9/11 Commission Act in 2007, DHS said, which resulted from an internal probe of the circumstances surrounding the September 11, 2001 attacks on the United States.

The ESTA rules do not affect US travelers heading overseas.

Asked if the United States would oppose a reciprocal policy imposed on American citizens traveling to Europe, State Department Sean McCormack said Washington would have no objections.

"The European Commission has discussed publicly creating its own electronic travel authorization system and we would not oppose the creation of such a system," he said.

The visa waiver program was created in 1986 "with the objective of eliminating unnecessary barriers to travel, stimulating the tourism industry," according to the State Department website.

The Travel Industry Association told AFP that the new program "is good for travelers," but noted "the travel community believes a significant and expansive communications effort is needed to fully explain this new system to our friends" in affected countries.