By Basil Katz

NEW YORK (Reuters) - A U.S. judge will decide on Thursday whether a New York lawyer convicted of helping a terrorism suspect smuggle messages to his followers from prison should spend 30 years behind bars instead of 28 months.

Lynne Stewart, 70, has been imprisoned since November on charges she helped her client, blind Egyptian cleric Sheikh Omar Abdel-Rahman, contact the Islamic Group in Egypt, which the U.S. government lists as a terrorist organization.

Stewart, who was convicted by a jury in July 2005 and has been disbarred, was sentenced to 28 months in prison by a judge who noted her long career defending the poor, as well as her willingness to take up difficult cases for little pay.

U.S. prosecutors seeking a 15- to 30-year sentence appealed the decision and the case was sent back for resentencing.

Abdel-Rahman was convicted in 1995 of conspiring to attack the United Nations and other New York City landmarks, following the 1993 World Trade Center truck bombing. The twin towers were later toppled in the September 11 attacks of 2001 carried out by al Qaeda.

Lawyers for Stewart said in court filings the original sentence should be maintained as it takes into account her age, that she has cancer and that her actions caused no harm.

Prosecutors argued that Stewart's crimes were terrorism-related and should be subject to a harsher sentence.

"A sentence of 28 months for Stewart, a defendant who conspired with and materially assisted terrorists who were striving to kill people outside the United States and only through fortuity failed in achieving their murderous objectives would plainly be unreasonably lenient," they said.

"The fact that no innocent people were actually injured or killed as a result of Stewart's actions was not for lack of effort by Stewart, her co-defendants and their terrorist confederates."

During her trial, Stewart said she had been targeted because of her political beliefs. Stewart supporters were due to gather on Wednesday to march near the Manhattan courthouse.

(Editing by Doina Chiacu)