Washington, July 23 - An American who converted to Islam and fought for the Al Qaeda before his arrest in Pakistan last year is now cooperating with authorities, opening a rare window into the shadowy world of the terror network, American media reports said Thursday.

Bryant Neal Vinas, a 26-year-old from Long Island, New York, is one of the few Americans known to have made the trek to Al Qaeda's secret Pakistani compounds, US and European anti-terrorism officials told the Los Angeles Times.

He pleaded guilty in January to conspiring to murder US nationals, providing material support to Al Qaeda and receiving military training from the group, the New York Times reported.

Vinas has admitted to meeting Al Qaeda bosses and giving them information about New York commuter trains for a possible attack -- conversations that resulted in a public alert in November, said the officials, who requested anonymity.

He was captured by Pakistanis in November and is in custody in the US. He pleaded guilty in January to charges including conspiracy to commit murder for firing on US troops and providing material support to a terrorist organisation, the Los Angeles Times reported.

His court indictment was unsealed Wednesday after repeated queries about Vinas from the Los Angeles Times. Until then, the case had been a closely guarded secret at the heart of investigations in at least seven countries, the report said.

The US-born son of immigrants from Peru and Argentina, Vinas was raised a Catholic and his transformation into a fighter nicknamed Bashir el Ameriki (Bashir the American) underscored fears that some other Americans had followed the same route, the newspaper reported.