A former college professor accused of being Palestinian Islamic Jihad’s leader in America has reached a plea deal with prosecutors under which he would be deported after pleading guilty to a charge that he conspired to aid a terrorist group, an attorney involved in the case said yesterday.

Sami Al-Arian and three other men were put on trial in federal court in Tampa, Fla., last year on a variety of charges stemming from an alleged conspiracy to provide political and financial support to Palestinian Islamic Jihad, a group that has claimed responsibility for killing dozens of people in Israel, the Gaza Strip, and the West Bank, often through suicide bombings.

After hearing nearly six months of testimony, the jury acquitted Mr. Al-Arian in December on eight of the charges he faced. Jurors deadlocked on nine other counts. Some press reports said a majority of the jurors wanted to acquit Mr. Al-Arian, a former computer-engineering professor at the University of South Florida, on all charges.

A lawyer who represented Mr. Al-Arian at the trial, William Moffitt, said yesterday that he believed a judge was to be asked to approve the deal late last week. “It was supposed to go forward,” Mr. Moffitt said in a brief interview from a Washington hospital where he is recuperating from knee surgery.

Word of the plea deal came first on Friday from the Associated Press and additional details appeared in subsequent accounts in the Tampa Tribune and St. Petersburg Times. The Times said Mr. Al-Arian was planning to plead guilty to a count of the indictment that accused him of “conspiracy to make and receive contributions of funds, goods, or services to, or for the benefit of specially designated terrorists.” The charge Mr. Al-Arian was to admit to involved a claim that he aided Palestinian Islamic Jihad by interfering with efforts to deport his brother-in-law, Mazen Al-Najjar, who was removed from America in 2002.

A New Jersey man whose 20-year-old daughter was killed in an Islamic Jihad attack in 1995, Stephen Flatow, said he was satisfied with the plea arrangement given the difficulties prosecutors encountered in last year’s trial. “We’re just getting further and further away from the truth and the original evidence, which just makes it harder,” he said.

Mr. Flatow said that if Mr. Al-Arian has conceded his illegal involvement with a terrorist group, it is something of a victory for his critics. “He had earlier said there was no way he was going to plead to a terrorism charge,” Mr. Flatow, who testified at the trial in Tampa last year, said.

There were indications that Mr. Al-Arian entered the plea before a federal judge on Friday, but the court’s docket shows no public notation of such an event. However, the docket does reflect a recent flurry of activity in the case with at least 11 sealed filings in the past few days.

Change-of-plea hearings are usually held in open court. Legal observers said it was unclear why Friday’s proceedings went forward behind closed doors.

“It would be unusual to do something like that in secret,” a former terrorism prosecutor, Andrew McCarthy, said. He said pleas from cooperating witnesses are sometimes taken in secret, but that would not apply in this instance.

The secrecy may have been sought by defense attorneys on the grounds that if the judge rejected the arrangement, jurors at a future trial might consider the attempted plea evidence of Mr. Al-Arian’s guilt. His lead attorney, Linda Moreno, did not return calls seeking comment for this article.

A conspiracy charge carries a possible jail sentence of up to five years, though a shorter term is usually imposed. Mr. Al-Arian has been in pre-trial custody since he was arrested more than three years ago and would be entitled to have that time credited against any sentence.

About seven years elapsed between the execution of a search warrant at Mr. Al-Arian’s Tampa-based Palestinian Arab think tank and his arrest in 2003. The delay was due in part to legal strictures on sharing of intelligence with criminal investigators. Still, “the government did permit him to continue to do what he was doing,” Mr. McCarthy said. “It’s hard to argue that there’s a compelling need for an offender like this to do lots of jail time.”

Mr. McCarthy said the deportation would be a bitter pill for some because it means Mr. Al-Arian will be free to pursue his agenda abroad. “He could end up in the Palestinian territories. For all I know, he could become the functional equivalent of secretary of state over there,” the lawyer said.

Some suspected terrorists have gone on to become high-ranking terrorist leaders after being deported from America, but Mr. Flatow said Mr. Al-Arian has likely “outlived his purpose for Islamic Jihad.”