Al-Kassar is accused of selling millions of dollars worth of weapons to the Revolutionary Armed Forces of Colombia (Farc), a group classified in the US as a terrorist organisation.
The two other men, Tareq Mousa al Ghazi and Luis Filipe Moreno Godoy, were arrested as part of the same investigation.
An indictment unsealed in New York on Friday said the men had agreed to provide the weapons for the Farc "to use to protect their cocaine-trafficking business and to attack United States interests in Colombia".
Garcia told a news conference: "They knew the weapons they agreed to sell were destined for a terrorist organisation. They knew the arms were going to be used to kill Americans."
The three men are also charged with conspiracy to kill US nationals, conspiracy to kill officers and employees of the US, conspiracy to acquire and use anti-aircraft missiles, and money laundering.
|"They knew the weapons they agreed to sell were destined for a terrorist organisation. They knew the arms were going to be used to kill Americans" |
Prosecutors said al-Kassar and Ghazi met two confidential sources working with the US Drug Enforcement Administration at al-Kassar's home in February and discussed the sale of weapons to the Farc.
Al-Kassar, who is also reportedly on the Iraqi government's most-wanted list for allegedly arming anti-government fighters, went before a Spanish judge in Madrid on Friday.
A longtime Spanish resident known as the "Prince of Marbella" for his opulent lifestyle, al-Kassar has previously sold weapons to the Palestinian Liberation Front, Nicaragua, Bosnia, Croatia, Iran, Iraq and Somalia since the 1970s, the US embassy in Madrid said.
In 1995, he was acquitted by Spain's high court of a charge of piracy in connection with the 1985 hijacking of the Italian cruise liner Achille Lauro by Palestinian fighters.