Police were to question Prime Minister Ehud Olmert on Friday for a second time in a corruption case that threatens his political survival and Israeli efforts to advance fragile peace moves with Syria and the Palestinians.

Also Friday, a court was due to decide whether to grant a request by Olmert's lawyers to delay the court deposition of the chief witness in the case. Police suspect Olmert illicitly took up to half a million dollars in cash from the witness, American Jewish businessman Morris Talansky.

The investigation is still in progress, and no charges have been filed against Olmert. But detectives and state prosecutors are exploring the possibility he took bribes, violated campaign funding laws and laundered money, police have said.

Olmert has acknowledged taking money from Talansky for political campaigns, but said his campaign finances were the responsibility of a longtime confidant, who was questioned again on Thursday. The Israeli leader has denied wrongdoing and vowed to resign if indicted.

Police were scheduled to interrogate the prime minister on Friday for an hour in his Jerusalem residence. He was last questioned two weeks ago, for a similar length of time.

Talansky, who insists he received nothing from Olmert in exchange for the money, has been questioned by police and is scheduled to give a court deposition on Sunday. He is anxious to return to the U.S. immediately thereafter, his attorney, Jacques Chen, has said.

But Olmert's defense team wants to put off the testimony, saying it needs more time to prepare to cross-examine Talansky.

It is the fifth police investigation of Olmert's conduct since he became prime minister two years ago. All of the cases involve activities that took place before he became Israel's leader. No charges have been filed and one of the cases has been closed.

But the multiple probes have led to demands that the already unpopular Olmert resign and called into question his ability to conclude a peace deal with the Palestinians by a year-end target, or pursue recently confirmed peace talks with Syria.