NEW YORK - A Vietnamese man accused of plotting with an al-Qaida offshoot to bomb London's Heathrow Airport in a suicide attack should get 50 years in prison, prosecutors said in papers submitted Tuesday to a sentencing judge.

Minh Quang Pham, 33, faces sentencing May 16 after pleading guilty to terrorism charges in January. Pham, extradited from England, admitted supporting al-Qaida in the Arabian Peninsula, a Yemen-based branch of the organization once headed by Osama bin Laden.

The Heathrow plot was never carried out. Pham was arrested at the airport when he returned in July 2011 from a six-month trip to Yemen, where he used his college degrees in graphic design and animation to edit videos and photos for propaganda in Inspire magazine, prosecutors said.

In urging a long sentence, the government said Pham's intellect, cleverness and ability to recruit like-minded individuals will still be valued by terrorists.

"Indeed, the fact of his conviction and imprisonment likely will serve in many respects to bolster Pham's bona fides as a recruiter of others to wage violent jihad," prosecutors said.

In her presentence submission, Pham attorney Bobbi Sternheim said her client has denounced terrorism, never intended to commit violence and shouldn't serve over 30 years in prison, especially since solitary confinement will result in hopelessness and despair.

"Pham was directed byothers,had no specific missionand took no substantive terrorist actions, violent or otherwise," she wrote.

Prosecutors urged Judge Allison J. Nathan to "reject Pham's self-serving, unsworn, and unsubstantiated statements submitted in an 11th-hour effort to mitigate the seriousness of his actions."

The government noted that Dzhokhar Tsarnaev, convicted in the April 2013 attack near the finish line of the Boston Marathon, told the FBI that he and his brother learned how to create their pressure-cooker bombs from Inspire magazine.

Prosecutors said al-Qaida in the Arabian Peninsula has called on followers to attack civilians and has taken credit for co-ordinating attacks overseas, including the January 2015 Paris massacre at the French publication Charlie Hebdo. A dozen people died.

Prosecutors said Pham also received instruction and direction in Yemen from U.S.-born, extremist Islamic preacher and al-Qaida leader Anwar Al-Awlaki, who was killed in a drone attack in Yemen in September 2011.

They said Al-Awlaki had directed Pham to detonate explosives made with household chemicals in the arrivals area of Heathrow International Airport where U.S. citizens and Israelis arrive. They said Al-Awlaki specifically instructed Pham to tape bolts around the bomb to act as shrapnel.

News from © The Associated Press, 2016