Former Israeli prime minister Ehud Olmert on Friday made his first court appearance on charges of graft, vowing he would prove his innocence.

As the first Israeli premier to face criminal charges in court, Olmert acknowledged at the arraignment hearing in Jerusalem that he understood the charges against him. He is not scheduled to enter a plea until later this year.

Olmert resigned under pressure last September but has insisted on his innocence and told journalists on Friday he was confident the trial would vindicate him.

"I am innocent, and I am certain the court will clear me of any suspicions," he said. "It is not an easy day for me; for the past three years I have been the target of an almost inhuman defamation campaign."

The court decided it will start hearing testimony on February 22 and will hold three sessions a week.

Olmert, who turns 64 on Wednesday, was charged in August with three counts of graft.