The Pentagon was expected to submit to Congress on Tuesday President Barack Obama's long-awaited plan for closing the US military prison at Guantanamo, Cuba.

Obama, whose pledge to shut the facility at the US naval base dates back to the start of his presidency in 2009, is seeking to make good on his plan before he leaves office in January.

Pentagon spokesman Captain Jeff Davis said the administration intended to meet Tuesday's deadline for sending Congress a proposal for closing the facility. There are still 91 prisoners detained there.

US officials have said the plan would call for sending to their homelands or third countries detainees who have been cleared for transfer and bringing remaining detainees to US soil to be held in maximum-security prisons.

The Pentagon has sent assessment teams to some facilities to determine whether they are suitable to house detainees, including a high-security federal prison in Florence, Colorado, a military jail at Fort Leavenworth, Kansas, and the Navy brig at Charleston, South Carolina.

The blueprint being submitted to US Congress will include an estimate of the cost of closing the prison and upgrading US prison facilities.

The White House last year rejected one Pentagon proposal as too expensive and sent it back for revision.

US officials said the plan calls for up to $475 million in construction costs that would ultimately be offset by as much as $180 million per year in operating cost savings.

AP - Reuters