Israeli President Shimon Peres Friday asked right-wing leader Benjamin Netanyahu to form Israel's next government.
Mr. Netanyahu, who has served as prime minister in the past, immediately called on Foreign Minister Tzipi Livni and Defense Minister Ehud Barak to join him in what he called "a broad national unity government."
Livni, who had hoped to become prime minister herself, has shown little interest in joining Mr. Netanyahu's government. Officials say the two rivals may meet on Sunday to discuss the situation.
Mr. Netanyahu will have six weeks to put together a government. If Livni refuses to join him, he will most likely form a coalition of nationalist and religious parties that take a much more hardline approach to possible peace talks with the Palestinians.
A spokesman for the Palestinian militant group Hamas in the Gaza Strip said Mr. Netanyahu's nomination does not point to security and stability in the region in the days ahead.
Palestinian officials aligned with Hamas rival and Palestinian President Mahmoud Abbas said they will not deal with a future Israeli government that does not accept the establishment of an independent Palestinian state and continues the construction of Jewish settlements.
A U.S. State Department spokesman said Friday the United States would continue to work with its close ally Israel, and that the U.S. remained optimistic about achieving peace in the Middle East.
In remarks after his nomination, Mr. Netanyahu did not mention peace talks and instead said he views Iran as the greatest threat to Israel's security, reviving a familiar refrain from his campaign.
Friday's announcement came after Mr. Peres met separately with Mr. Netanyahu and Livni, whose Kadima party won one more seat than Mr. Netanyahu's Likud in parliamentary elections earlier this month but did not have enough support to form a government on its own.