U.S. President Barack Obama on Tuesday proposed to "once and for all" close the detention centre at Guantanamo Bay, Cuba, and transfer remaining detainees to a facility in the United States, saying that despite significant political hurdles and congressional opposition he is making one last effort to shut the controversial facility.

"I don't want to pass this problem on the next president, whoever it is. Are we going to let this linger on for another 15 years?" he said, in an appearance at the White House. "Keeping this facility open is contrary to our values. It undermines our standing in the world. It is viewed as a stain on our broader record of upholding the highest standards of rule of law."

Obama's proposal ducks the thorny question of where the new facility would be located and whether Obama could complete the closure before he leaves office.

There are currently 91 detainees at Guantanamo Bay. Of those, 35 are expected to be transferred out by this summer.

At its peak in 2003, Guantanamo held nearly 680 detainees, and there were about 245 when Obama took office.

Donald Trump, basking in a third straight win in the Republican Party race for nominee Tuesday in Nevada, vowed to keep Guantanamo open.

Trump told supporters gathered at the Treasure Island hotel in Las Vegas, "We're going to load it up with a lot of bad dudes out there."

Obama's plan, which requested by Congress, makes a financial argument for closing the controversial detention centre. U.S. officials say it calls for up to $475 million US in construction costs that would ultimately be offset by as much as $180 million per year in operating cost savings.

The proposal is part of Obama's last effort to make good on his unfulfilled 2008 campaign vow to close Guantanamo and persuade lawmakers to allow the Defence Department to move nearly 60 detainees to the U.S. But with few specifics, the proposal may only further antagonize lawmakers who have repeatedly passed legislation banning any effort to move detainees to the U.S.

Rep. Mac Thornberry, a Texas Republican and chairman of the House armed services committee, has said his panel would hold a hearing on a closure plan. But he sent a letter to Obama warning that Congress has made clear what details must be included in any plan and that anything less than that would be unacceptable.

Obama Guantanamo

President Barack Obama speaks in the Roosevelt Room of the White House on Tuesday. (Pablo Martinez Monsivais/Associated Press)

U.S. officials say the plan considers, but does not name, 13 different locations in the U.S., including seven existing prison facilities in Colorado, South Carolina and Kansas, as well as six other locations on current military bases. They say the plan doesn't recommend a preferred site and the cost estimates are meant to provide a starting point for a conversation with Congress.

The seven facilities reviewed by a Pentagon assessment team last year were: the U.S. Disciplinary Barracks and Midwest Joint Regional Corrections Facility at Leavenworth, Kan.; the Consolidated Naval Brig, Charleston, S.C.; the Federal Correctional Complex, which includes the medium, maximum and supermax facilities in Florence, Colo.; and the Colorado State Penitentiary II in Canon City, Colo., also known as the Centennial Correctional Facility.

According to the officials, the U.S. facilities would cost between $265 million and $305 million to operate each year. The annual operating cost for Guantanamo is $445 million, but the officials said the Cuba detention centre will need about $225 million in repairs and construction costs if it continues to be used.

Guantanamo Who's Left

In this Feb. 2, 2016 photo, a detainee is seen in the communal area inside Camp 6 in the U.S. detention center at Guantanamo Bay, Cuba. (Ben Fox/Associated Press)

They said it will cost between $290 million and $475 million for construction at the various U.S. sites, depending on the location. Some of the more expensive sites are on the military bases, which would need more construction. Because of the annual operating savings, the officials said the U.S. would make up the initial construction costs in three to five years.

More detailed spending figures, which are considered classified, will be provided to Congress, said the officials, who were not authorized to discuss the plan publicly ahead of its release, so spoke on condition of anonymity.

Late last year, other U.S. officials said that the assessments done by the Pentagon team suggested that the Centennial Correctional Facility in Colorado is a more suitable site to send detainees whom officials believe should never be released. Those officials were not authorized to discuss that matter publicly, so spoke on condition of anonymity.

Members of Congress have been demanding the Guantanamo plan for months, and those representing South Carolina, Kansas and Colorado have voiced opposition to housing the detainees in their states.

"I remain committed to blocking the transfer of Guantanamo detainees anywhere in the United States, especially Fort Leavenworth," Senator Jerry Moran, R-Kan., said in a statement Tuesday. "We must safeguard the missions on Fort Leavenworth, the nearly 14,000 military and civilian personnel and their family members, and the thousands of Kansans who live in the Leavenworth community."

Blocked by law 

The administration is currently prohibited by law from moving Guantanamo Bay detainees to the United States. Obama has long opposed that prohibition and the White House has not ruled out the possibility that the president may attempt to close the prison through executive action. The plan submitted Tuesday does not address that option, officials said.

Advocates of closing Guantanamo say the prison has long been a recruiting tool for militant groups and that holding extremists suspected of violent acts indefinitely without charges or trial sparks anger and dismay among U.S. allies.

Opponents, however, say changing the detention centre's zip code won't eliminate that problem.

"We'll review President Obama's plan," Republican Senate majority leader Mitch McConnell said. "But since it includes bringing dangerous terrorists to facilities in U.S. communities, he should know that the bipartisan will of Congress has already been expressed against that proposal."

Paul Ryan, the Republican Speaker of the House of Representatives, said Obama had yet to convince Americans that moving the prisoners to the United States was smart or safe.

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