The Department of Homeland Security yesterday awarded a contract worth up to $10 billion to Accenture LLP to oversee and expand a massive U.S. program to track millions of foreign visitors as they cross American borders.

The project, called U.S. Visit, collects and stores information about foreigners entering and exiting the country on visas through airports and seaports. The data, including digital photographs and fingerprints, are stored in an electronic database and shared among some government agencies to ensure that visitors do not overstay their visas and to help authorities capture suspected terrorists and criminals.

The program debuted at U.S. airports and seaports in January and has processed more than 4.5 million people. Homeland Security officials said they have used U.S. Visit to deny entry to suspected terrorists and to arrest more than 500 wanted or suspected criminals.

Now the program will expand to track all foreign visitors entering and exiting the country, including those who don't need visas and those who arrive by land.

Accenture will oversee or replace a number of government contractors that are working on the existing pieces of the U.S. Visit program, which began under the former Immigration and Naturalization Service. The company's task will be to vastly broaden the project to visitors crossing land borders without slowing international commerce. About 94 percent of all foreign visitors enter and exit the country by land.

"I don't think you could overstate the impact of this responsibility, in terms of security of our nation," said Asa Hutchinson, undersecretary for Border and Transportation Security at the Department of Homeland Security. "If you look at the 9/11 terrorists, they came here in violation of our immigration laws."

Some critics complained that Reston-based Accenture LLP should not have won the contract over its competitors, Lockheed Martin Corp. and Computer Sciences Corp., because its parent, the consulting firm Accenture Ltd., is based in Bermuda. "Accenture isn't contributing its fair share to the costs of the very contract that it's now been given," because of the tax advantages it receives, said Rep. Lloyd Doggett, a Texas Democrat who has authored a bill to eliminate incentives for American companies that move their headquarters abroad.

Homeland Security's Hutchinson said yesterday that Accenture LLP is a U.S. taxpayer and is qualified to bid on U.S. government contracts. He said the agency chose Accenture based on its management and technical ability, its past performance on government contracts and the amount of its bid.

Officials yesterday declined to provide the total value of the five-year contract, saying it would range from $10 million to $10 billion, depending on how much funding the program receives from Congress, the agency's policy decisions and Accenture's performance. Homeland Security officials said Accenture bid $72 million to complete the first year's work.

Accenture will help Homeland Security meet two ambitious deadlines. By Dec. 31, Homeland Security must begin fingerprinting and photographing foreigners who enter the country at the 50 busiest land borders. A Homeland Security spokesman said that initially most Canadians and Mexicans will be exempt from the program, but eventually all Mexicans and Canadians may have to comply. By Dec. 31, 2oo5, the program will be extended to all land crossings.

Some vehicles crossing land borders are already equipped with radio frequency tags that transmit data about the driver, including photographs, to immigration and customs officers, much as EZPass technology works at tollbooths. Homeland Security officials envision eventually using similar technology to allow drivers and passengers to transmit their personal information instantly while crossing the border.

Under Accenture's plan, U.S. Visit would create "virtual" folders for each foreign traveler entering by air, sea or land that would electronically store visa application information, fingerprints, photographs, entry and exit dates, and the purpose of the visits. For travelers with a student visa, for example, the folder would also include relevant details such as the school and period of enrollment.

"They selected us because we had a clear understanding for their vision of the future of border management for this country," said Eric Stange, Accenture's managing partner for defense and homeland security.

Accenture will create a chief privacy officer because the system will give inspectors unprecedented access to travelers' personal information. Originally conceived as an immigration program, U.S. Visit is now being designed to integrate immigrations databases and to share information about millions of foreigners with a host of federal and state agencies.

The program will enable Homeland Security officials to share information about individuals with the Departments of Justice, Transportation and Commerce and the FBI. Officials said they would only share information with other agencies as part of a specific criminal investigation or "authorized purpose," such as the agency's Citizenship and Immigration Services, which processes citizenship applications.

David L. Sobel, general counsel for Electronic Privacy Information Center, said the government should be more clear about the conditions under which it shares people's information. "The large-scale collection and sharing of information is a serious concern," he said. "Its always inevitable that once one agency has a large collection of information, it's really only a matter of time [before] that information" is sent throughout the government.

The contract is the largest yet awarded by the 18-month-old Homeland Security agency and is widely seen as a stepping stone to other big department contracts.

The U.S. Visit program received $367 million for fiscal 2003 and has received $340 million for fiscal 2004.

"That's why all of these companies are working so hard to really try to win these contracts," said Philip Finnegan, an analyst for the Teal Group, a defense research firm. "They all really see homeland security as a bit of a wild card but a real potential growth area."

Accenture's team comprises 29 subcontractors, including AT&T Corp., Dell Inc. and KBR, a subsidiary of Halliburton Co.