Washington, Jan 5 - A federal appeals court has upheld the sentence of life in prison without parole against Zacarias Moussaoui, a conspirator in the Sep 11, 2001, terrorist attacks on New York and Washington.

Moussaoui, who has been in a maximum-security prison in Colorado since 2006, argued that the government did not turn over classified evidence that could have aided his defence.

The US Court of Appeals for the Fourth Circuit, based in Richmond, Virginia, rejected that argument and upheld his conviction Monday.

Moussaoui, a French citizen of Moroccan descent, pleaded guilty in 2005 to six counts of conspiracy relating to the Sep 11 attacks that killed nearly 3,000 people. The plea, which was entered against the advice of his court-appointed lawyers, guaranteed him a sentence of life in prison without the possibility of parole.

After a federal jury failed to impose the death penalty in 2006, Moussaoui tried to withdraw his guilty plea and reduce his life sentence, claiming a new-found faith in the US justice system. (dpa)