Tel Aviv - Members of Israel's ruling Kadima party is choosing a new leader Wednesday to replace discredited Prime Minister Ehud Olmert.

Some 74,000 registered members of the centrist party are eligible to vote at 114 polling stations placed in 93 different locations throughout the country.

Polls are scheduled to open 10 am (0700 GMT) and close 12 hours later, with initial results expected in by midnight. Israel's main television channels, however, are expected to broadcast the results of exit polls shortly after voting ends.

Four candidates are taking part in the race: Foreign Minister Tzipi Livni, Transportation Minister Shaul Mofaz, Public Security Minister Avi Dichter and Interior Minister Meir Sheetrit.

Livni, 50, has been leading solidly in the polls throughout the campaign, but Mofaz, 60, has said his campaign is better organized and able to mobilize activists to get the vote out for him.

He has even produced his own study, which contradicts published opinion polls and predicts he will win 43.7 per cent of the vote.

Dichter and Sheetrit, for their part, are trailing far behind in the opinion polls.

Candidates need at least 40 per cent of the vote to win in the first round. If no one does, a second round will be held Wednesday next week.

Olmert, 62, is being investigated over suspicions of corruption and on Sunday last week police recommended he be indicted, a final decision on which has yet to be made by Israel's attorney-general.

The embattled premier agreed to hold the Kadima primary after coming under pressure from his largest coalition partner, the Labour Party, and has announced he will resign immediately after the winner of the party leadership contest is announced.

His successor will then try to form a new coalition government, but if he or she fails, early elections by March 2009, a year ahead of schedule, are likely.

Olmert, whose resignation will take effect 48 hours after submission to the president, could nonetheless stay on at the head of a transitional government until then, or until the new coalition is formed.

Livni's aides have said they want Olmert to take a leave of absence or declare himself temporarily unable to carry out his duties, allowing her to take over even at the head of the transitional government before then.

But an aide to Olmert, speaking on condition of anonymity to Israel's Ma'ariv daily, vowed the premier had no intention of allowing his Kadima successor to head the transitional government.

"So long as there is a transitional government, he (Olmert) will head it," said the aide.

The primary is essential for the peace negotiations with the Palestinians, as Livni, Israel's chief negotiator, has said she will continue the talks according to their current format, while hawkish contender Mofaz wants to postpone talks on the core issues of the Israeli-Palestinian conflict and on a final peace deal.

Mofaz, a former army chief of staff and defence minister who is highlighting his security credentials, also calls for tough action against Palestinian militants.

Olmert agreed with Palestinian President Mahmoud Abbas late last year to end a seven-year freeze in the Middle East peace process and try to reach a shelf peace agreement by the end of the year.

Chief Palestinian negotiator Ahmed Qureia however told officials of his Fatah party late Monday he did not believe the deadline could still be met.

Official results of the primary are expected early Thursday. (dpa)