Blue and White party leader Benny Gantz has failed to form a new government by the deadline, dashing his hopes of toppling longtime Prime Minister Benjamin Netanyahu and pushing Israel closer to an unprecedented third election in less than a year.
It has shaken Israelis' confidence as conflicts with Iran and Syria deepen, and vexed a usually friendly White House.
According to Israeli law, a sitting prime minister does not have to resign until a final conviction, after exhausting all appeals.
"We have made great efforts toward forming a broad, liberal unity government... a government that will serve everyone - religious and secular, Jews and Arabs".
In his speech Wednesday, Lieberman said that he had held talks with Netanyahu and Gantz in recent days, but that both the incumbent and aspiring prime minister had attempted to make coalitions including "anti-Zionist" parties - referring to the Ultra-Orthodox Jewish parties Netanyahu has long courted, as well as Gantz's attempts to rally to his cause leaders of the Palestinian community of Israel.
Incumbent leader Netanyahu's right-wing Likud party and former military general Gantz's centrist Blue and White coalition were almost deadlocked after September elections, with neither able to command a majority in Israel's 120-seat parliament.
Gantz for his part accused Netanyahu of intransigence.
Europe is to blame for the lack of peace talks between Israel and the Palestinians, the Jewish state's United Nations envoy. "I turned over every stone", he said.
Gantz's announcement that he could not meet the deadline set by President Reuven Rivlin doesn't automatically trigger new elections.
Lieberman said: 'As things stand now, we are on the way to another election'.
Ahmed Tibi, a senior politician from Israel's 21 percent Arab minority, tweeted that Lieberman's rhetoric constituted "incitement" and "straight-up racism and anti-Semitism".
Earlier Wednesday, former defense minister Avigdor Lieberman, who heads a smaller political party, refused to endorse either Gantz or Netanyahu, dooming prospects for breaking the deadlock.
Attorney General Avichai Mandelblit is due to decide by December whether to charge Netanyahu over a series of graft accusations he denies.
Neither Netanyahu nor Gantz have the required majority to build a coalition government.
Rivlin, among many others, has pleaded with the sides to find some sort of compromise to avoid another costly and divisive election campaign and even offered a power-sharing plan in which Gantz and Netanyahu would rotate as prime ministers.
Should tonight's deadline expire without a coalition deal, a 21-day period will begin in which legislators can nominate any lawmaker, subject to the agreement of at least 61 of parliament's 120 members and a formal mandate from Rivlin, to try to establish a coalition.