By Nate Raymond

NEW YORK (Reuters) - A Yemeni man who prosecutors said was a member of al Qaeda and engaged in attacks against U.S. military forces stationed in Iraq and Afghanistan pleaded guilty on Tuesday to conspiring to kill Americans overseas.

    Saddiq al-Abbadi, 40, pleaded guilty in federal court in Brooklyn, New York, to four counts including conspiracy to murder U.S. nationals abroad and conspiracy to provide material support to a foreign terrorist organization.

Al-Abbadi, who appeared in court with a black beard and wearing blue jail clothes said that during the period in question, "I and others agreed to provide material support to al Qaeda."

The plea came after prosecutors in January unveiled charges against al-Abbadi and another Yemeni man, Ali Alvi al-Hamidi. Both men had been arrested in Saudi Arabia and were subsequently expelled.

Al-Abbadi faces up to life in prison. U.S. District Judge Nicholas Garaufis scheduled sentencing for Sept. 25. His lawyer declined to comment after the hearing.

Prosecutors have said that al-Abbadi fought against U.S. military forces in Iraq between 2003 and 2007, before traveling with Al-Hamidi to Pakistan in 2008 to train and fight with al Qaeda.

In mid-2008, al-Abbadi and al-Hamidi traveled from Pakistan to separate parts of Afghanistan to conduct attacks against the U.S. military, prosecutors said.

Al-Abbadi led at least two separate attacks against U.S. forces in Pakistan's Paktya province, including one in May 2008 in which a U.S. Army Ranger died and several others were wounded, prosecutors said.

The pair also helped Bryant Neal Vinas, a Long Island, New York, man, join the Islamic militant group, prosecutors said in court documents. Vinas pleaded guilty in 2009 to helping al Qaeda plan an attack on the Long Island Rail Road.

Al-Abbadi had been a longtime member of al Qaeda, prosecutors said, and engaged directly with its senior leadership, including Abu Saeed al-Masri, its former third-ranking member who was killed in 2008.

Al-Abbadi was previously convicted in Saudi Arabia for plotting an al Qaeda attack there, and served 5-1/2 years of a 12-year prison sentence, according to court records.

Charges are pending against al-Hamidi, 30, who pleaded not guilty in February to five counts including conspiracy to murder U.S. nationals abroad and providing and attempting to provide of material support to a foreign terrorist organization.

(Reporting by Nate Raymond in New York; Editing by Noeleen Walder, Richard Chang and Leslie Adler)