(Thomas Reuters Foundation) * Alone rivals each lack parliamentary majority * Incumbent PM has pre-trial hearing next month (Adds statement after Netanyahu-Gantz meeting) Prime Minister Benjamin Netanyahu and his rival Benny Gantz launched negotiations on Monday over a proposed Israeli unity government and a key politician said the focus was on who would lead it first under a rotation deal. After failing to secure a clear victory in the second election in six months Netanyahu Israels longest-serving premier seems to reckon he can stay in power only by sharing it. Going solo neither he nor ex-general Gantz have enough support from respective allies for a majority in the 120-member parliament. Gantz head of the centrist Blue and White Party has been publicly resistant to the idea of allying with Netanyahus right-wing Likud citing looming corruption charges against the incumbent. President Reuven Rivlin tasked with picking a candidate best-placed to try to form the next governing coalition has spoken in favour of unity and on Monday summoned Netanyahu and Gantz for closed-door talks.