Israeli centre-left leader Isaac Herzog ruled out Wednesday prospects of a unity government with Benjamin Netanyahu, the day after losing a general election to the right-wing prime minister's Likud party.
"Going into opposition is the only realistic option facing us," he told a meeting of his Zionist Union party in Tel Aviv.
After polls last week showed a growing lead for the Zionist Union, which allies Herzog's Labour party with the centrist HaTnuah of Tzipi Livni, results Tuesday showed Likud turning the tables and securing 30 seats in the 120-member parliament to the Zionist Union's 24.
Netanyahu, who won a third consecutive term, and his fourth overall, spoke overnight to rightwing and religious party leaders with whom he intends to form a ruling a coalition, the Likud said.
Under Israel's electoral system, the prime minister is not the leader of the party that gains most seats but whoever can build a coalition commanding a majority of at least 61 seats in parliament.
"We shall continue to lead a large and strong camp that wants a Jewish, democratic, secure and just state," Herzog said.
"The fight is not over yet," Livni said.
"We cannot give up. We must fight for our way, also in opposition."