(AP) - Authorities revealed Wednesday that an American- charged with giving al-Qaida information on the New York transitsystem and attacking a U.S. military base in Afghanistan - has beena secret witness in the fight against terror both here andoverseas.

Court papers unsealed in federal court in Brooklyn identifiedthe defendant as Bryant Neal Vinas, also known as "Ibrahim."

His identity had been kept secret since his indictment late lastyear. Court papers indicate that he pleaded guilty in January in asealed courtroom in Brooklyn.

Federal prosecutors refused to discuss his background Wednesday.But a law enforcement official, speaking on condition of anonymitybecause the official was not authorized to discuss the case, saidVinas provided critical information that led to a security alertabout the New York City subway system last year.

Federal authorities issued an alert around Thanksgiving lastyear saying the FBI had received a "plausible butunsubstantiated" report that al-Qaida terrorists in late Septembermay have discussed attacking the subway system around the holidays.The origin of that report, the offical said, was Vinas.

The official described Vinas as a militant convert who wascaptured last year in Pakistan.

Prosecutors charged Vinas in a rocket attack on U.S. forces inAfghanistan in September 2008. Court papers allege he also gave"expert advice and assistance ... on the New York transit systemand Long Island Railroad."

For five months last year, Vinas received "military-styletraining" from al-Qaida, according to court papers.

Also, a defense attorney in a terrorism case in Belgium saidprosecutors there traveled to New York earlier this year tointerview Vinas. The lawyer said Vinas had provided a statementagainst the French and Belgium defendants charged with going toPakistan to volunteer to fight with al-Qaida.

Vinas' defense attorney didn't immediately return a telephonemessage Wednesday.

Public records indicate that Vinas is originally from LongIsland. A woman who answered a phone number associated with hisfamily in Patchogue said she was his mother and had not seen herson since he moved out 10 years ago at age 18.

"He's a stranger to me," she said before hanging up withoutgiving her name.

In sealing the courtroom for the January guilty plea, a judgesaid that a public plea could harm a confidential investigationinvolving national security.

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