Tzipi Livni has become Israel’s opposition leader in the Knesset as part of a deal agreed with Avi Gabbay’s Labour Party.
Ms Livni has agreed that her Hatnuah Party will again run in the next parliamentary elections in the Zionist Union electoral alliance with Labour.
But Israeli media said the terms of the alliance had not been unannounced and it remains unclear which party leader would be the bloc’s candidate for prime minister.
The next election must be held before November 2019.