WASHINGTON >> The Pentagon’s plan outlining the long-stalled effort to close the Guantanamo Bay detention center, expected in the coming week, includes details suggesting that the Centennial Correctional Facility in Colorado is one suitable site to send detainees whom officials believe should never be released, administration officials said.

The plan represents a last-gasp effort by the Obama administration to convince staunch opponents in Congress that dangerous detainees who can’t be transferred safely to other countries should be housed in a U.S.-based prison.

According to administration officials, the plan makes no recommendations on which of seven U.S. sites is preferred and provides no rankings. But it lists the prison sites in Colorado, South Carolina and Kansas that a Pentagon assessment team reviewed in recent months and mentions advantages and disadvantages for the facilities. Those elements can include the facilities’ locations, costs for renovations and construction, the ability to house troops and hold military commission hearings, and health care facilities.

The Centennial facility has advantages that could outweigh the disadvantages there, according to officials, but no details were available and no conclusions have been reached. The officials spoke on condition of anonymity because they weren’t authorized to discuss the matter publicly.

Any decision to select a U.S. facility would require congressional approval — something U.S. lawmakers say is unlikely. At the same time, dangerous prisoners are not new to Colorado. The Supermax in Florence, Colorado, which has been dubbed "Alcatraz of the Rockies," already holds convicted terrorists, including Unabomber Ted Kaczynski and Zacarias Moussaoui, one of the conspirators of the Sept. 11, 2001, attacks.

The Pentagon plan also lays out the broader effort to reduce the detainee population at Guantanamo, through transfers to other countries. The center now holds 112 detainees, and 53 are eligible for transfer. The rest are either facing trial by military commission or the government has determined that they are too dangerous to release but are not facing charges.

In order to approve a transfer, Defense Secretary Ash Carter must conclude that the detainees will not return to terrorism or the battlefield upon release and that there is a host country willing to take them and guarantee they will secure them.

As President Barack Obama heads into his final year in office, the effort is part of a push to keep his election promise to close the detention center at Guantanamo Bay, Cuba. But he is facing an uphill battle with Congress.

Sen. John McCain, R-Ariz., has asked for an administration plan for the shutdown of Guantanamo. The Pentagon’s assessment team visits over the last few months were part of the effort to provide options for the relocation of Guantanamo detainees.

"I’ve asked for six and a half years for this administration to come forward with a plan – a plan that we could implement in order to close Guantanamo. They have never come forward with one and it would have to be approved by Congress," McCain said this week.

The facilities reviewed by the assessment team were the U.S. Disciplinary Barracks and Midwest Joint Regional Corrections Facility at Leavenworth, Kansas; the Consolidated Naval Brig, Charleston, South Carolina; the Federal Correctional Complex, which includes the medium, maximum and supermax facilities in Florence, Colorado; and the Colorado State Penitentiary II in Canon City, Colorado, also known as the Centennial Correctional Facility.

A Colorado senator made it clear this week that he opposes any move to relocate detainees to his state.

"I will not sit idly by while the president uses political promises to imperil the people of Colorado by moving enemy combatants from Cuba, Guantanamo Bay, to my state of Colorado," Republican Sen. Cory Gardner told a Capitol Hill news conference.

Later, Gardner told The Associated Press that "the pressure that this would put on our judicial system in Colorado is real. The challenges that could be brought through the legal system we’re not prepared for. I think that’s another question on our federal judiciary in Denver. This is a rural area of Colorado. Would they be transported to downtown Denver to the federal courthouse for a hearing?"

Even as the White House pitches this latest plan to skeptical lawmakers, officials have not ruled out the possibility that Obama will try to close the prison and move the remaining prisoners to the U.S. without congressional approval.

"I would not take anything off the table in terms of the president doing everything that he can to achieve this critically important national security objective," White House spokesman Josh Earnest said this week, when asked whether Obama would act unilaterally. "And this is a pretty transparent case of the United States Congress putting narrow political interests ahead of national security."

The threat echoes Obama’s moves on immigration and gun control — both cases where he urged Congress to pass legislation and then used his executive authority when the bills failed.

McCain and others have said that an executive order to shutter Guantanamo would face fierce opposition, including efforts to reverse the decision through funding mechanisms.

The prison at Guantanamo presents a particularly confrontational replay of that strategy. Obama would likely have to argue that the restrictions imposed by Congress are unconstitutional, although he has abided by them for years. The dispute could set off a late-term legal battle with Republicans in Congress over executive power, potentially in the height of a presidential campaign.