Feinstein, vice chairman of the Select Committee on Intelligence of the Senate, stated that instead of blocking President Barack Obama's efforts to close the prison, the Capitol should help him to achieve that goal.

The lawmaker stated that she visited the prison in 2002 and 2013, where she could confirm the urgent need to close it as it "costs us billions of dollars and is a real threat to our national security".

She also stated the prison is currently one of the best instruments of propaganda of the terrorists, who use it to justify their actions and recruit new members. And, on the other side "our allies criticize us because that center is a violation to the state law.

Feinstein added that the cost per detainee there is about $2.5 million USD a year, about 30 times higher than the $86,374 spent on an inmate in a maximum security prison in Supermax, Colorado state.

In January 2002, Washington opened the detention center in Guantanamo Bay, facility located in Cuban territory against the will of the people and government of the island.

During the administration of George W. Bush (2001-2009) 779 individuals were incarcerated there, even when no criminal charges were filed against them.

Currently 112 are still there, of which 53 are authorized to leave when a proper destination is found for them, according to official reports.

About 30 are captive indefinitely, 10 are in various stages of a process for alleged war criminals and 22 do not face any criminal charges and await a review of a group of national security experts.

Since taking his first term in January 2009, Obama promised to close the prison in Guantanamo Bay but the president faces serious obstacles in Congress.