A new US plan to close the military prison in Guantanamo Bay, Cuba, is likely to be unveiled in the coming days, with much at stake not only for President Barack Obama but also his counterterrorism chief, Lisa Monaco.

As a top Justice Department official in 2009, Monaco was summoned to the White House Situation Room in the first weeks of Obama's tenure to discuss how to fulfill his campaign promise to close a facility that had drawn condemnation worldwide.

Nearly seven years later, most of those who were present at that first meeting have left the government, but Monaco is still there and charged with completing the unfinished task.

The new plan, which will follow previous attempts that have failed, would mothball a prison that Obama views as a damaging symbol of detainee abuse and detention without charge that he inherited from Republican President George W Bush.

Senior administration officials told Reuters the plan would be unveiled in early November.

Obama, a Democrat, is adamant that Guantanamo be shut down before his successor takes over in 2017, giving Monaco, 47, one of the biggest challenges of her career.

"I can't say with certainty that we're 100 per cent going to get there, but I can tell you we're going to die trying," said Susan Rice, Obama's national security adviser, in an interview.

Monaco has laid out the plan's key elements. It would transfer eligible detainees to foreign countries; prosecute those who can be prosecuted; and move foreign terrorism suspects who cannot be prosecuted but are deemed too dangerous to release to a US-based facility, an option that is now barred by law.

That approach, and Monaco's stewardship of it, has plenty of critics. Lawmakers such as Republican Senator John McCain are frustrated with the long delay in addressing the issue. Human rights activists are irritated by the prospect of moving detainees to US soil without formal charges being brought against them.

Monaco declined to be interview for this article.

"I'm certain that Lisa shares the president's frustrations on the lack of progress toward closing Guantanamo, but at the same time the White House just hasn't taken the actions necessary to move forward," said Raha Wala, senior counsel at Human Rights First.

It has been up to Monaco, who sometimes drolly answers "peachy" when asked how she is, to get the Departments of Defense, State, and Justice to back the plan while helping to persuade lawmakers to accept it.

Lawmakers recently approved a defence bill that limited transfers from the prison. Obama vetoed it, but Republicans are sticking with those provisions.

'Occasional friction'

Pentagon delays over clearing prisoners for transfer has been another challenge that Monaco has worked to overcome. Two high-profile transfers occurred in the last week.

"Despite some occasional friction [among agencies], we're working very well to come together around a common point of view. And she deserves enormous credit for that," Rice said of Monaco.

Former colleagues say Monaco's institutional knowledge of Guantanamo has helped her guide the process of finding consensus on how to close the prison.

"She's intimately familiar with all of these discussions that have come before," said former White House counsel Kathryn Ruemmler. "That just gives you a huge advantage."

Monaco became Obama's homeland security and counterterrorism chief in 2013, experiencing what Ruemmler called a "trial by fire" with the Boston Marathon bombing shortly after her arrival in the job.

Her brief today extends far beyond Guantanamo, encompassing cyber security, Ebola, and the militant group Islamic State, policy areas that some critics say have seen mixed success.

The new "Gitmo" plan may face a rough road. A White House official said it contains no "silver bullet" and does not endorse a specific US facility for receiving 50 or so prisoners determined to be part of an "irreducible minimum" that cannot be let go. Some 112 prisoners are held at the prison now, down from 242 when Obama came into office.

In the end, Monaco may need her boss' help to get Republican approval for a domestic detention facility.

"There's a limit to what even a shrewd negotiator or professional like Lisa can do," said Phillip Carter, a former Pentagon official who worked on detainee policy in 2009. "Some of these things will have to be resolved by the president and members of Congress directly."