A U.S. senator who backs closing the Guantanamo Bay detention center says a new study shows there is clearly capability to hold the remaining 166 inmates being held there at U.S. prisons.

But the Obama administration, while reiterating its desire to close the controversial facility, too, said the Thomson Correctional Center, where it once wanted to house those detainees, will hold only inmates in the U.S. prison system.

Sen. Dianne Feinstein, D-Calif., who chairs the Senate Intelligence Committee, asked for the study, which was conducted by the Government Accountability Office. She said Wednesday that it makes clear the U.S. prison system can hold Gitmo detainees “if the political will exists” to close the facility.

Closing Guantanamo Bay has long been a goal of President Barack Obama, but bipartisan opposition has stopped him. Congress has passed measures that prevent money from being spent to move Gitmo detainees to U.S. soil, and they continue to be on the books. The administration has opposed those measures and did so again this week in a veto threat of a defense policy bill pending in the Senate. Those kind of warnings have been given before, however.

A senior administration official said Thursday it is “continuing its efforts to close the facility.” But the official appeared to dash any notion it sees an opportunity to so so quickly.

“With the current legislation in place, it is clear that it will take some time to close the detention facility,” said the official, who spoke on the condition of anonymity. As for Thomson, the official said, “the entire facility will only house (Bureau of Prisons) inmates.”

Republican critics in Congress who have been suspicious, particularly where Thomson is concerned, renewed their skepticism. Rep. Frank Wolf, R-Va., who has said purchase of the Thomson prison could be the first step toward moving the detainees, reacted to the new GAO report by saying he’s troubled it was “kept secret” until Thursday.

A spokesman for Feinstein said she asked for the study in 2008 and had not discussed the matter with the president, according to the Miami Herald. Its release was delayed two weeks because it was received as Gen. David Petraeus was testifying before Congress about the attack in Libya, the newspaper reported.

The transfer of ownership of the Thomson facility to the federal government has been completed, according to a Federal Bureau of Prisons spokesman. Meanwhile, a spokeswoman for Sen. Dick Durbin, D-Ill., reiterated that Durbin is on the record opposing moving Gitmo detainees to Thomson.

“This is about bringing jobs to Thomson,” Christina Mulka, the spokeswoman, said.

The GAO’s 68-page study said it was not passing judgment on whether any specific facility was suitable, and it did not mention Thomson. It said it was describing the facilities at Guantanamo Bay, as well as facilities and factors to be considered if U.S. prisons were to be used in the future to hold detainees. The report also noted the Justice Department said it was not preparing for any transfer.