Washington ? Atty. Gen. John Ashcroft was in a hospital intensive care unit Friday after suffering a severe case of gallstone pancreatitis, a serious and painful abdominal illness.

Ashcroft, a 61-year-old former Missouri senator and governor, was being treated with antibiotics. The ailment often clears up after a week or so of treatment but sometimes requires surgery. In extreme cases, it can cause death.

Doctors at George Washington University Hospital said they needed more time to evaluate Ashcroft and make a prognosis. It’s possible Ashcroft could remain hospitalized for a month or more, medical experts said.

President Bush spoke briefly with Ashcroft by telephone Friday afternoon, White House press secretary Scott McClellan said.

“Our thoughts are with the attorney general,” McClellan said in Crawford, Texas. “We wish him a speedy recovery.”

Under Justice Department rules, Deputy Atty. Gen. James Comey is authorized to exercise “all power and authority” of the attorney general. No transfer of power is necessary.

Ashcroft initially thought his sudden sickness was a stomach flu. But he began feeling so ill Thursday afternoon that he canceled an appearance at a news conference where he was to announce terrorism convictions.

After returning to his Capitol Hill home, his condition worsened and he was examined by Dr. Daniel Parks, the White House physician, said Justice Department spokesman Mark Corallo. Parks advised Ashcroft to go to an emergency room, and the attorney general was taken to the hospital Thursday evening.

“After a full medical work-up in the emergency room, it was determined that he was suffering from a severe case of gallstone pancreatitis,” Corallo said.

Pancreatitis is an inflammation of the pancreas, a gland that secretes digestive enzymes and insulin. The two main causes are alcohol abuse and, as in Ashcroft’s case, a gallstone that blocks the passage from the pancreas to the beginning of the small intestine. It also may be caused by infection, injury or certain medications.

The illness also often occurs when a gallstone becomes lodged in the passage that leads from the pancreas to the small intestine. Symptoms include sudden, severe abdominal pain, loss of appetite, nausea, vomiting and fever.