A 26-year old American man who converted to Islam at a Long Island mosque has been charged with joining Al Qaeda and taking part in a rocket attack on a US base in Afghanistan.

A 26-year-old American-born Long Island man who traveled to Pakistan and trained in a Qaeda camp there last year has been charged with taking part in a rocket attack against a United States base in Afghanistan, according to court papers unsealed on Wednesday.

The man, Bryant Neal Vinas, who was arrested in Peshawar, Pakistan, last November, was also charged with assisting Al Qaeda by providing “expert advice and assistance” that was “derived from specialized knowledge of the New York transit system and the Long Island Rail Road, communications equipment and personnel,” according to the papers.

The court papers, a criminal information charging Mr. Vinas with conspiracy and carrying out the attempted missile attack, providing material support to Al Qaeda and receiving military support from the group, did not mention a specific New York City plot involving the Long Island Rail Road. The papers, filed by prosecutors in the office of the United States attorney in Brooklyn, Benton J. Campbell, also say that Mr. Vinas attempted the attack and received “military-type training” from and on behalf of Al Qaeda between March and August 2008.

But around the time of his arrest in Pakistan in November, the federal authorities in New York issued warnings about a possible attack on mass transit. One official said that the information about the possible attack, which the authorities described at the time as “aspirational,” came from a Long Island man who had been arrested in Pakistan.

The criminal information charges that Mr. Vinas, along with other people who were not named, “fired rockets at a United States military base in Afghanistan” in September 2008.