A Yemeni man plans to plead guilty to piracy next week for his role in the hijacking of a yacht off the coast of Africa that left four Americans dead, his attorney said Thursday.

Mounir Ali's attorney, Jim Theuer, said Ali would plead guilty to the charge in federal court on Monday as part of a plea deal with prosecutors.

Like the 10 Somalis in the case who pleaded guilty before him, Ali is expected to cooperate with the government as it prosecutes the three Somali men identified as the shooters aboard the sailing vessel and the man accused of being the pirates' chief negotiator. No other men have outstanding charges.

The owners of the Quest, Jean and Scott Adam of Marina del Rey, Calif., along with friends Bob Riggle and Phyllis Macay of Seattle, were shot to death several days after being taken hostage several hundred miles south of Oman.

Court documents accuse the men of hijacking the yacht with the intention of ransoming the Americans once they got back to Somalia. The plan fell through when four American warships started shadowing them. Negotiations with the U.S. Navy were under way when shots were fired aboard the boat.

Hostages are typically held for ransoms for millions of dollars. The Somali pirates said they intended to split the money among themselves and with an interpreter, while an unnamed financier would get 35 percent of the money.

Records show Ali was originally on another boat that the Somalis had taken hostage. But he willfully chose to join the Somalis after they captured the American vessel in hopes in sharing in the profits.

The Adams had been sailing full-time on their 58-foot yacht since December 2004 after retiring. Around Christmas, the Quest joined the Blue Water Rally, an around-the-world race. But race organizers said the Americans had left the race before the hijacking.

Others pirates in the case have said they boarded the yacht while it sat still in the water and the Americans were sleeping.