Israeli Foreign Minister and newly-elected ruling Kadima party leader Tzipi Livni last night officially received a presidential mandate to form a new government.

Upon the authorization, the 50-year-old woman politician called on all the other parties, including the main opposition party Likud, to join a national unity government under her leadership.

"I agree to take upon myself the role of forming a government," Livni told President Shimon Peres at a brief ceremony at the presidential residence in Jerusalem, vowing to embark on the task solemnly.

Earlier, the mainly ceremonial president formally informed parliament Speaker Dalia Itzik of his choice, which was made after he had consulted with leaders of all the 13 factions in the parliament.

By law, Livni, the third and the first woman leader of the Kadima party has 28 days, with a possible extension of 14 days, to set up her own cabinet, which has to gain endorsement of the Knesset (parliament).

Should she fail, Peres may assign the mission to a second and even a third lawmaker, or inform the parliament that no new government can be formed. If the cabinet-making efforts prove to no avail, early general elections will be held, possibly in the spring.

If she succeeds, the former agent of the Mossad intelligence agency will replace Ehud Olmert and become the 13th premier in Israel's history.

She has already taken over the leadership of the three-year-old centrist party from Olmert after winning the party's primary last week.

The official authorization came a day after the outgoing premier, dogged by a series of police probes, submitted his resignation letter to Peres.

Yet till the formation of a new government, whether by a lawmaker or after early general elections, Olmert will remain in power as caretaker prime minister.

Upon accepting the cabinet-making mission, the lawyer-turned political figure expressed gratitude to her predecessor for resigning in a respectable way, who has promised to support her in the bid to form a new government.

NATIONAL UNITY GOVERNMENT

Livni told a press conference following the ceremony that the "first and right choice" for Israel is a stable government that will serve until the end of the term of the current Knesset.

Actually, since winning out in the primary, the would-be second woman prime minister, following Golda Meir, has already been pushing forward her cabinet-making efforts, and has vowed to set up a government as soon as possible.

Noting that recent days are not normal for Israel, which is facing great diplomatic and economic challenges, Livni called on the current ruling coalition parties to remain together under her leadership, while urging other parties, including the hardline Likud, to join her line.

However, opposition leader Benyamin Netanyahu, a former prime minister, has categorically ruled out the possibility to be part of Livni's government, while trying to persuade other parties to support holding snap elections.

Recent polls predicted that the Likud party, to which all the three Kadima leaders had been affiliated before former Prime Minister Ariel Sharon founded the new party in late 2005, would emerge as the largest winner should snap elections were held today.

Although being the largest party in the parliament, Kadima has only 29 out of the 120 seats, and it thus has to rule in the form of a coalition government.

The Labor Party, both as the second largest with 19 seats and as a current ruling partner, is apparently an option Livni would not easily give up.

In a move that could significantly increase her chances of success, Livni received a promise from Labor Chairman and Defense Minister Ehud Barak, who is also a former premier, that his party would cooperate with Kadima to make serious efforts to form a new government.

Although it is still not clear whether the Labor would join a Livni-led government, local daily Ha'aretz reported that Livni andher aides did not think Barak was in any hurry to hold general elections.

Another current coalition partner, the Shas Party, also poses a threat to Livni's efforts, as the right-wing party has vowed that it will not sit in a government that would make concessions on the Jerusalem question in negotiations with the Palestinians.

Analysts say that Livni would gather some other small parties under her flag to offset the possible breakaway of the Shas or Labor.

"I have every confidence in my ability to lead the State of Israel, with the full, honest and genuine cooperation of all the parties invited to join the coalition, for the sake of the State of Israel and its citizens," said Livni.