JERUSALEM — Ariel Sharon, the former prime minister of Israel who has been comatose for nearly eight years, edged closer to death on Wednesday evening, suffering from kidney failure.

A spokesman for the hospital that has been treating Mr. Sharon, 85, said that “there has been a deterioration in his medical condition.” A person who had been briefed on the situation, but spoke on the condition of anonymity because of its delicacy, said Mr. Sharon had suffered a setback about a month ago and spent two weeks in intensive care after emergency surgery, then seemed to have stabilized before the most recent turn.

“It looks pretty bad, but it’s not a matter of hours,” said another person with knowledge of his situation who also spoke on the condition of anonymity.

Mr. Sharon, a controversial military commander who rose to hold many of his nation’s top positions, suffered a stroke after shaking up Israeli politics at the height of his power.