CHICAGO - The Obama administration announced yesterday it would move some terrorism suspects from Guantanamo Bay, Cuba, to a state prison in rural Illinois, though officials acknowledged they would need congressional support to fully implement the transition and had no timetable for the transfer.

The site will be toughened into a facility that exceeds "supermax standards," Secretary of State Hillary Rodham Clinton, Defense Secretary Robert M. Gates, Homeland Security Secretary Janet Napolitano, Attorney General Eric H. Holder Jr., and Director of National Intelligence Dennis C. Blair said in a letter to Illinois Gov. Pat Quinn.

Administration officials would not say how many of the 210 detainees at Guantanamo would be sent to the Thomson Correctional Center, but White House press secretary Robert Gibbs said he would not contradict an estimate by Sen. Richard J. Durbin (D., Ill.) of 100.

Overall, 116 detainees have been cleared for release by a review team led by the Justice Department. The administration is trying to resettle these detainees in third countries, but the pace of transfers has been slow - just 31 since Obama took office.

The Justice Department will use part of the facility, 150 miles west of Chicago, to house federal inmates, while the Defense Department will use part to house a "limited number" of Guantanamo detainees.

Officials said that detainees would not be permitted visits by family or friends, would be guarded by military personnel, would not mix with federal inmates, and would not be released on U.S. soil.

But even as top administration officials declared the security of the facility of paramount concern, Republican leaders condemned the widely anticipated decision, saying it would create an unacceptable risk.

"The Obama administration is putting international public relations ahead of public safety," Rep. Mike Pence of Indiana, the No. 3 House GOP leader, said.

The administration also drew fire from civil-liberties groups and detainees' attorneys, who questioned Obama's proposal to hold some prisoners in Illinois indefinitely without trial.

Amnesty International USA, asserting that detainees should not be held in Thomson without charges, said "the only thing that President Obama is doing with this announcement is changing the zip code of Guantanamo."

The selection of a U.S. prison to succeed Guantanamo is an essential component of Obama's plan to fulfill a campaign promise and close a detention center that has become a global symbol of Bush administration policies that were seen as unduly harsh.

The White House national security adviser, James Jones, said shifting detainees to Thomson would make the United States more secure and remove "a recruiting tool that Guantanamo Bay has come to symbolize" for terror organizations.

Illinois Democrats pushed for the selection of Thomson, arguing that a federal purchase of the $145 million prison, built in 2001 but now home to fewer than 200 minimum-security inmates, would produce as many as 3,000 jobs in a region with unemployment topping 11 percent.

In response to doubts raised by Rep. Mark Steven Kirk (R., Ill.), the Pentagon reported yesterday that 1,000 to 1,500 personnel would move to the Thomson area to operate the military side of the prison once it is upgraded. About two-thirds would be members of the uniformed military, while about one-third would be civilians.

"It's a wonderful thing," Thomson real estate agent Jeannine Mills said. "We certainly need the economic boost."

Renovations at the facility are likely to take six months or more, administration officials said. Congress will be asked to approve funding and to repeal a law that prohibits detainees from being incarcerated on U.S. soil for reasons other than trial.

Some of the Guantanamo detainees moved to Thomson would likely be tried by military commissions that would operate on the 146-acre facility, officials told reporters.

Apart from new security measures, the prison is expected to need a courthouse for trials, an improved medical facility and a kitchen staff trained to prepare religiously appropriate meals for the Muslim inmates.

Prisoners scheduled for transfer to U.S. allies overseas will go directly from Guantanamo, an official said, while detainees scheduled for trial in U.S. District Courts will be held in nearby detention facilities.