TEL AVIV (Reuters) - Prime Minister Benjamin Netanyahu’s toughest rival in Israel’s April ballot, a popular ex-general, vowed on Tuesday to pursue peacemaking and clean government in swipes at the premier, but did not rule out forming a coalition with him.

In a long-awaited speech in which he broke his silence for the first time since joining the campaign, former military chief Benny Gantz was careful not to directly attack Netanyahu, who is under investigation for corruption.

Instead, he criticized what he described as a “divisive” leadership that was detached from the people, too concerned with hanging on to power and too loose with its tongue on matters of security.

“The mere notion that in Israel a prime minister can remain in office while under indictment is ridiculous,” Gantz said at a launch party timed to coincide with the evening TV news.

Netanyahu, who denies any wrongdoing, has said he is a victim of a political witch hunt and has lashed out at the police, the media and the left.

Israel’s attorney-general is presently weighing whether to charge Netanyahu in three corruption cases. Unlike others in the running, Gantz did not say he would not join a Netanyahu government in the meantime.

Polls predict that Netanyahu will win re-election, with his right-wing Likud party taking around 30 of parliament’s 120 seats, and Gantz’s Resilience party coming a distant second with around 15.

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That would line Gantz up to join a future Netanyahu-led coalition - unless the ex-general tries to mobilize other factions against the incumbent, who is now in his fourth term.

PEACE, SECURITY

Tamar Hermann, a scholar with the non-partisan Israel Democracy Institute, said that for Netanyahu to be defeated, Gantz would have to bring together disparate center-left parties.

“At the moment the most likely outcome of the election would be a (Netanyahu-led) center-right government,” she said.

Likud has sought to write Gantz off as a “leftist”, casting him as an untested whimsy candidate and no match for Netanyahu, 69, who is also defense minister.

As the election approaches Netanyahu has highlighted his handling of national security, publicly acknowledging Israeli air strikes against Iranian targets in Syria.

Appealing to hawkish voters, Gantz took a tough stance on Iran and its allies in Lebanon and Gaza: “In the difficult, violent Middle East no one pities the weak and only the strong prevail.”

But mindful of Israeli moderates, Gantz also said: “The government under my leadership will pursue peace and will not miss a chance to effect a regional change.”

Martin Dempsey, a retired U.S. army general whose tenure as chairman of the Joint Chiefs of Staff mirrored that of Gantz as Israeli armed forces chief between 2011 and 2015, told Reuters he believed Gantz would bring “an open mind to change” and have the “instincts to build a team to solve the most urgent challenges”.