Israeli president Shimon Peres has given prime minister Benjamin Netanyahu an additional 14 days to try to form a new government, after he was unable to complete the task during an initial 28-day period.
Talks with potential partners have been deadlocked since elections on January 22, and if he is unable to form a government by March 16, a new poll could be called.
Netanyahu's Likud party, which ran on a joint ticket with the ultra-nationalist Yisrael Beitenu, won 31 of the Knesset's 120 seats, a diminished lead that forced him to cast a wide net for partners while juggling their demands.
During the 28-day period, Netanyahu managed to forge a pact only with the party of former foreign minister Tzipi Livni, whose six-member Hatnuah ("The Movement") has given him 37 seats, far short of the minimum 61 needed to confirm a new coalition.
In a brief statement following his meeting with Peres on Saturday night, Netanyahu hinted that at least one potential coalition partner refused to sit alongside others.
Netanyahu has faced demands from the parties that placed second and fourth, Yesh Atid ("There is a Future") and Bayit Yehudi ("Jewish Home"), to slash mass exemptions from military conscription and cut welfare stipends to ultra-Orthodox Jews.
The two parties have formed an alliance, and vowed not to enter the coalition unless Netanyahu agrees to their demands.
In coalition talks on Friday with Bayit Yehudi, Netanyahu's chief negotiator said the right-wing party was unwilling to sit alongside ultra-Orthodox parties, but Bayit Yehudi officials denied this.
Although he did not name Bayit Yehudi or Yesh Atid as the reason for his failure to form a coalition, Netanyahu said some parties were boycotting others.
"In these past four weeks I tried to form the broadest possible government. I think the ultra-Orthodox public is prepared to accept [demands by other partners] but the main reason that I have not managed to complete the task by today is because there is a boycott of a certain sector," he said.
Netanyahu's outgoing coalition includes two ultra-Orthodox parties which have generally backed him on policies such the settlement of occupied West Bank land, in defiance of world powers who support the Palestinians' drive for statehood there.
Bayit Yehudi is even less accommodating of the Palestinians than Netanyahu, who says he wants to revive stalled peace talks.