JERUSALEM - Police began questioning 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.

While Olmert was being questioned in his Jerusalem residence, a court was considering a request by Olmert's lawyers to delay the court testimony of a 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 longtime confidant Uri Messer, who was questioned again on Thursday. The Israeli leader has denied wrongdoing and vowed to resign if indicted.

National Fraud Squad investigators 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.

The allegations span a 12-year period beginning in the 1990s when Olmert was mayor of Jerusalem and extending through his tenure as minister of industry and trade, which ended in 2006, police have said. Police have raided city hall and the ministry, carting away documents as part of their investigation.

Talansky insists he received nothing from Olmert in exchange for the money, but police suspect otherwise. On Friday, the Maariv newspaper reported that investigators were examinating allegations that when serving as trade minister, Olmert asked an Israeli diplomat in an unidentified South American country to ask for assistance in promoting an unspecified technological project in which Talansky was a partner.

Last week, the Yediot Ahronot newspaper reported he sought favors from Olmert on behalf of associates.

Police have said privately that Messer has given police documents and oral testimony that strengthen their suspicions that the money Olmert received was earmarked for his personal use - and donated in expectation of future assistance.

Talansky had little to say on the new developments, referring questions to his lawyer, Jacques Chen. But he dismissed as "nonsense" and "ridiculous" a Jerusalem Post newspaper report Friday citing a group of right-wing rabbis who said they pushed him to testify in the case to bring down Olmert. The rabbis are afraid he will cede sovereignty over holy sites in east Jerusalem, the sector of the city the Palestinians want as capital of a future state, the newspaper said.

Chen wasn't immediately available for comment.

Talansky has been questioned by police and is scheduled to testify under oath on Sunday. He is anxious to return to the U.S. immediately after testifying, 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.

The investigation is the fifth into Olmert's conduct since he became prime minister two years ago. 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.