An Adelaide-raised former accountant is facing a 20-year imprisonment sentence by a US court for conniving with and aiding the terror group a-Qaeda.

On June 18, Sabirhan Hasanoff, 37, will be sentenced by a Manhattan court after being found guilty of "providing material support, including financial support, equipment and technical advice, to al-Qaeda." He is set to serve a 20-year maximum statutory sentence.

Hasanoff is an Australian-US citizen who lived in Brooklyn, New York. He used to work as an accountant for top accounting firms such as PricewaterhouseCoopers.

As an al-Qaeda devotee in New York, he was considered the best person to undertake surveillance for "The Doctor" and "Suffian," aliases of two al-Qaeda affiliated leaders who are based in Yemen.

In the 47-page sentencing memorandum, the prosecutors detailed how Hasanoff carried out his covert mission for the two terror leaders by scouting the New York Stock Exchange.

The "Doctor," a self-confessed jihadist, contemplated on attacking the stock exchange headquarters, according to prosecutors.

As the designated lookout, the former accountant took the task of making notes outside Wall Street, including exact location in Manhattan, the size of the property and its installed security system.

Hasanoff allegedly gathered everything he saw into a one-page email and sent the information to "Suffian."

Investigation revealed that the email contained details of how the stock exchange headquarters was strategically located. Hasanoff related how it was surrounded by four streets all closed to vehicular traffic, and how such condition required any attack to be done on foot.

The e-mail was reportedly printed out by "Suffian" and was given to "The Doctor" who in turn was not impressed. The terror leader was apparently disappointed as the surveillance work did not contain the information he was looking for.

The details, however, satisfied US authorities and were enough to press Hasanoff for the charges filed against him.

"The offence conduct in this case is enormously serious - providing material support to al-Qaeda that included money, technical advice and equipment sought by the terrorist group to engage in further violence against Americans, and surveilling a potential target in New York City for a domestic terrorist attack," assistant US attorney Glen Kopp told US District Court Judge Kimba Wood.

"Against this backdrop, it is frankly hard to see why a lenient, below-guidelines sentence would be appropriate here."

Also in the memorandum are the prosecutors' information on Hasanoff's relationship with the "Doctor" and "Suffian" and his desire to undergo jihad training in Pakistan.

Hasanoff was arrested in 2010 while staying in the United Arab Emirates. He was nabbed in UAE together with another Brooklyn-based Wesam El-Hanafi, and both were brought back to the US for trial.