WASHINGTON — The Pentagon is expected to submit to Congress on Tuesday President Barack Obama’s long-awaited plan for closing the U.S. military prison at Guantanamo, setting up a battle with lawmakers who oppose his efforts.

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

Pentagon spokesman Capt. 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.

“We understand the deadline is tomorrow and it’s our intent to meet it,” Davis told a media briefing on Monday. “We’re working on it and intend to submit it soon.”

U.S. 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 U.S. 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.

An effort would also be made to speed up parole-style reviews to determine whether more prisoners can be added to the group cleared for release, which would reduce the final number who might eventually be brought to American soil.

The blueprint being submitted to Congress will include an estimate of the cost of closing the prison and upgrading U.S. prison facilities, according to a source familiar with the matter. The White House last year rejected one Pentagon proposal as too expensive and sent it back for revisions.

Republicans and some Democrats in Congress largely oppose proposals to move any of the prisoners to the United States, an option currently prohibited by law.

Republican Sen. Kelly Ayotte of New Hampshire said in a statement Monday the Obama administration refused to “level with the American people regarding the terrorist activities and affiliations of the detainees who remain at Guantanamo.”

White House spokesman Josh Earnest urged legislators to look at the plan “with an open mind,” although he expressed doubt about whether they would do so.

The prison was opened in 2002 by then-President George W. Bush and quickly drew criticism from human rights activists and foreign governments.