WASHINGTON — A former Florida professor has not eaten for more than a month to protest prosecutors’ efforts to make him cooperate with their investigation into whether a network of Islamic charities based in suburban Herndon, Va., financed terrorist organizations.

Sami Al-Arian, 49, who has twice refused to testify before a federal grand jury in suburban Alexandria, Va., has lost more than 30 pounds and collapsed in jail from the effects of his water-only diet. His hunger strike has drawn the support of Islamic organizations, which held a news conference last week at Justice Department headquarters in Washington and called for a worldwide fast in support of Al-Arian.

Tracy Billingsley, a spokeswoman for the federal Bureau of Prisons, said prison officials will force-feed Al-Arian through a tube if he appears close to death. “We would not let an inmate die,” she said.

A federal jury in Tampa deadlocked in 2005 on nine charges that Al-Arian aided terrorists and acquitted him of eight other counts. He then pleaded guilty to one count of supporting a Palestinian Arab militant group. Sentenced to 57 months, including time already served, he was expected to be released from prison and deported this year.

But prosecutors want Al-Arian to testify in their probe into whether the network of Islamic charities, businesses, and think tanks was financing terrorist organizations, according to court documents. He has twice refused and been held in contempt by a federal judge. As much as 18 months could be added to his prison term unless he agrees to testify.

On January 21, Al-Arian stopped eating, supporters said. He has had only water since then, and on several days not that.

Federal marshals recently moved him from Northern Neck Regional Jail in Warsaw, Va., to a federal medical prison in Butner, N.C., federal officials and supporters said.

Al-Arian is trying to rally public support so prosecutors will stop trying to make him testify, said Agha Saeed, chairman of the American Muslim Taskforce for Civil Rights and Elections, a coalition of Islamic groups.

The former University of South Florida professor has accused prosecutors of violating his plea agreement with the Justice Department, which he contends does not require his cooperation.

“Why do they continue to humiliate and punish this man?” asked Nihad Awad, national executive director of the Council on American-Islamic Relations. “They exhausted all their resources and found out there is no case against him. Enough is enough.”

The U.S. attorney’s office in Alexandria, which is leading the Herndon probe, would not comment.

David Kelley, a former U.S. attorney who prosecuted terrorism cases in New York, said it is a common tactic for prosecutors to seek additional testimony from someone already convicted. “In many instances, you are remiss if you don’t pursue that,” he said.

A judge has rejected Al-Arian’s argument that he does not have to cooperate with Alexandria prosecutors under his plea agreement. “The Court has never heard of the Government agreeing that someone would forever be protected from grand jury subpoena,” U.S. District Judge James Moody wrote in November from Tampa.

On Wednesday, Al-Arian’s attorneys filed a notice that they will appeal the contempt findings to the U.S. Court of Appeals for the 4th Circuit in Richmond, said Ashraf Nubani, one of the attorneys.