"Closing the detention center at Guantanamo is essential to protecting our national security and helping our troops by removing a deadly recruiting tool from the hands of al Qaeda," the official said.

This "announcement is an important step forward as we work to achieve our national security objectives."

When Obama took office in January, he gave himself one year to close the prison. But Republicans and others criticized his administration's plans to transfer the prisoners to the United States and try them in civilian courts as a security risk.

Congress enacted a law barring Guantanamo detainees from being brought onto U.S. soil except if they were going to be prosecuted. Democrats, who control both houses of Congress, are planning to lift that restriction if the administration comes up with an acceptable plan for how to handle the prisoners.

A part the Illinois prison in a rural area west of Chicago would be used to house detainees from the naval detention camp in Guantanamo Bay, Cuba which was opened in 2002 to house suspects after the September 11, 2001 attacks.

The U.S. official said Illinois Governor Pat Quinn and Illinois Senator Dick Durbin will be in Washington on Tuesday to be briefed at the White House on the decision.

Durbin and Quinn said last week that the Illinois facility, which is mainly empty, would be turned into a federal maximum security prison, and a portion of it would be leased to the Defense Department to house some detainees.