The US government has charged two Yemeni nationals for allegedly conspiring to murder Americans abroad, and providing material support to al-Qaeda, according to a complaint and arrest warrant.

Saddiq al-Abbadi and Ali Alvi were arrested in Saudi Arabia and extradited to the US, the US Justice Department said on on Tuesday.

Alvi, 30, appeared in a federal court in Brooklyn on Sunday while Abbadi, 36, was scheduled to be arraigned on Tuesday afternoon, the department said.

The two Yemenis engaged in attacks against US forces in Afghanistan in the summer of 2008, and had travelled in March of that year to Pakistan to train and fight with al-Qaeda, prosecutors said in the complaint.

The pair also helped an American citizen join al-Qaeda, according to the complaint.

If convicted, both suspects could face life in prison, Al Jazeera's Kimberly Halkett reported from Washington DC.

Originally filed under seal in April 2009, the complaint describes a cooperating witness who travelled to Pakistan in 2007 with the intention of "waging violent jihad" against the US, and who was able to join al-Qaeda in Pakistan with the help of Abbadi and Alvi.

Trained in Pakistan

The witness, who previously pleaded guilty to conspiring to murder Americans abroad, providing material support to al-Qaeda, and receiving military-type training from the group, told prosecutors of training in Pakistan's tribal areas in a basic weapons course and advancing to explosives and projectile weapons training, according to the complaint.

The complaint also alleges that a second confidential source who travelled from Saudi Arabia to Iran and then to Pakistan corroborated information about the two Yemeni defendants.

Tuesday's news came as the US also announced that another man, Wesam el-Hanafi, had been sentenced to 15 years in prison in New York for "providing material support to al-Qaeda.

"Wesam el-Hanafi was deeply involved in supporting al-Qaeda both financially and by facilitating surveillance of a New York landmark to bring an attack to our homeland in our city," Preet Bharara, US attorney for the Southern District of New York, said.

"Today’s sentence is a fitting punishment for these crimes and we will continue, with our law enforcement partners, to pursue punishment for those who provide and conspire to provide material support for terrorists."

Source: Al Jazeera and agencies