The Obama administration will bypass the difficult political decision of selecting a single alternative U.S. site for the Guantanamo Bay, Cuba, detention facility when it sends Congress its much-anticipated plan for shuttering the controversial prison.

Deputy Defense Secretary Robert Work, whose department has been evaluating several prospective sites, told CQ he expects the administration to submit its plan within the next month. But rather than choosing one domestic facility to house the detainees still held at Guantanamo, Work said the report will include a menu of options and the costs associated with each of those.

That approach will fall flat with Senate Armed Services Chairman John McCain, who has been pushing the administration for months to submit a detailed roadmap for Guantanamo’s closure.

“They haven’t communicated that to me. But if that’s the case, that’s not a plan,” McCain said on Thursday. “That’s a wish. That’s a hope.”

The Arizona Republican has said he would try to sell the administration’s proposal to a reluctant Congress if he agrees with the plan. But before he endorses it, McCain wants a number of assurances, including that the prisoners be housed in a maximum-security facility run by the Defense Department.

“All we are trying to do is do our deliberative process to answer a question by the chairman of the SASC and provide him with that data,” Work said in an interview with CQ.

McCain said he would review the proposal when it comes to the Hill. But without specific details that he says the president once promised him, McCain said he won’t be able to sell the plan to his colleagues.

“The president of the United States, in the Oval Office, looked me in the eye and said , ‘We’ll have a specific plan for you,’” he added. “I’m used to presidents — I’ve dealt with other presidents — when they look you in the eye and tell you they’re going to do something, they usually do it.”

McCain’s version of the fiscal 2016 defense authorization bill (S 1376), which passed the Senate this summer, requires the administration to submit a plan, subject to congressional approval, for transferring the remaining prisoners at the facility to a maximum security prison within the United States.

The committee’s report on the bill suggests that they expect details on where those detainees would be transferred.

“Prior to authorizing the transfer of detainees into the United States the committee seeks a comprehensive plan that will describe the disposition of all detainees, including where each detainee will be held or transferred, the costs associated with continued detention, the legal risks of any transfer, and what additional authorities are needed,” the report states.

The stakes are undeniably high for Obama, who has tried and failed to sell Congress on shuttering Guantánamo since the outset of his first term.

Under McCain’s proposal, which is not yet law, Guantánamo would close if Congress approves the plan. But if lawmakers reject the administration’s proposal, the ban on domestic transfers would stay in place and heightened standards in the bill for foreign transfers would remain.

While it’s not clear whether House and Senate negotiators on the defense bill will sign off on his Guantánamo language, McCain has expressed frustrations that the White House has not yet seized on the opportunity provided in his bill.

But selecting a specific site is probably the most difficult part of shuttering Guantanamo, with lawmakers in potentially affected states already ramping up their not-in-my-backyard rhetoric.

The Pentagon is considering military sites in South Carolina and Kansas, drawing fierce opposition from those delegations. Officials are also weighing other non-military sites, but has not disclosed those.

“I’m not prepared to say what those sites are today because you see what happens – as soon as we announce a site, it becomes an issue,” Work told CQ.