Gantz,a former Israeli army chief who had vowed to bring Netanyahu's long rule to an end and fought him to a draw in three elections,said he was changing course to help bring the country together to fight the coronavirus pandemic.
"These are unusual times,and they call for unusual decisions,"Gantz said in a speech to parliament early Thursday evening.
"This is not the time for infighting and mudslinging,"he said."This is not the time for controversy and divisions. This is the time for responsible,committed,patriotic leadership. Let's join hands and get Israel out of this crisis."
The move was a 180-degree reversal and broke countless campaign promises by Gantz. Netanyahu has been indicted on criminal corruption charges,and Gantz had vowed not to serve in a government led by a prime minister under indictment.
Gantz said he would"explore the formation of a national emergency government"because of the coronavirus,which has claimed eight lives in Israel,infected thousands and devastated the country's economy.
Gantz's move immediately led to the breakup of his centrist Blue and White party.
He may also have doomed his own political future as a credible alternative to Netanyahu,some analysts said. Others said a unity government would offer Gantz his best chance at taking over as prime minister at some point in the future.