NEW YORK: A United States (US) citizen already accused of going to Pakistan to train with Al Qaeda was charged Wednesday with helping build explosives for a 2009 suicide attack on an American military base in Afghanistan.

A revised indictment charges Muhanad Mahmoud Al Farekh with conspiracy to murder US nationals, conspiracy to use weapons of mass destruction and other crimes.

He is to appear Thursday in federal court in Brooklyn. There was no immediate comment by his lawyer.

The charges stem from an attack on Jan 19, 2009, involving two vehicles driven by unidentified suicide bombers that were rigged with explosives, the new indictment says. Only one of the bombs detonated.

Al Farekh's fingerprints were later found on packing tape used on the second explosive, the indictment says. The court papers didn't identify the base or detail the damage incurred in the attack.

News accounts from the same 2009 date cited in court papers described a dual-car bomb attack at Forward Operating Base Chapman in Khost city, near the border with Pakistan, which killed one Afghan and wounded several others, but harmed no Americans.

The 30-year-old Al Farekh, who was born in Texas, "allegedly turned his back on our country and tried to kill US soldiers in the course of executing their sworn duty to keep us safe", Brooklyn US Attorney Robert Capers said in a statement.

Al Farekh was brought from Pakistan to the US in April to face initial charges of providing material support to terrorists.

Federal authorities alleged he and two other students at the University of Manitoba in Winnipeg, Canada, started watching Al Qaeda propaganda and hatching a plan to become militants abroad.

The three flew to Karachi, Pakistan, on round-trip tickets in March 2007 after selling their belongings, disconnecting their phones and buying mountain boots commonly worn by Al Qaeda fighters in Pakistan and Afghanistan, authorities said.

Prosecutors said one of Al Farekh's co-conspirators trained three men on how to use AK-47s and other weapons at an Al Qaeda training camp in 2008, the complaint says.

The three ─ Najibullah Zazi, Zarein Ahmedzay and Adis Medunjanin ─ were later convicted of plotting to bomb New York City's subway system and are cooperating with federal authorities.