9/11 lawyer says Trump 'serious' about using Guantanamo prison
Masked Guantanamo protesters kneel during the Democratic National Convention August 25, 2008 in Denver (Lilac Mountain / Shutterstock.com)

The lawyer of self-proclaimed 9/11 mastermind Khalid Sheikh Mohammed said on Monday he believes US President Donald Trump is serious about using Guantanamo Bay to house more "terrorist" suspects.

Defence lawyer David Nevin added that any chance of closing the notorious site had been lost with the end of Barack Obama's presidency.

"Our president said he intends to keep Guantanamo open and put more people there, and I took his words seriously," Nevin said at a Doha human rights conference.

Nevin added that he would take the president "at his word" after recent comments from Trump in which he vowed to fill Guantanamo with "bad dudes".

When Obama first came to power in 2009, he vowed to close Guantanamo's jail.

But after eight years in power, he failed to do so in the face of Republican opposition and the reluctance of US allies to take in the detainees.

The current population at the prison is 41.

Mohammed was recently in the news when it emerged he had sent Obama a letter telling him that the 9/11 attacks that killed almost 3,000 people were America's fault and a direct result of US foreign policy.

Since his arrest in 2003, Mohammed has been waterboarded 183 times and detained at a secret CIA prison site overseas.

He is currently being held in Guantanamo.