Three of the men accused of plotting the 11 September, 2001 terrorist attacks have entered into a pre-trial agreement, the US Department of Defence says.

Khalid Sheikh Mohammad, Walid Muhammad Salih Mubarak Bin Attash, and Mustafa Ahmed Adam al-Hawsawi have been held at the US Navy base Guantanamo Bay, Cuba, for years without going to trial.

According to US news outlets, the men will plead guilty in exchange for the prosecution agreeing not to seek the death penalty.

The terms of the plea deal have not yet been released.

Nearly 3,000 people in New York, Virginia and Pennsylvania were killed in the al-Qaeda attacks, which sparked the “War on Terror” and the invasions of Afghanistan and Iraq.