There will be something to discuss "when the prime minister reaches the conclusion that his policy of the last 16 months is leading Israel on the slope to an unnecessary war," said Barak.

His comments marked a slight shift from his previous opposition to a unity government.

Since replacing former Prime Minister Shimon Peres at the helm of the Labor Party in June, the former army chief of staff had dismissed the idea, calling the policies of the governing coalition a "failure."