JERUSALEM, Oct. 17 (Xinhua) -- Benny Gantz, Israeli centrist Blue and White party leader who won most seats in elections in September, rejected on Thursday a unity government proposal by incumbent Prime Minister Benjamin Netanyahu.

"Today I received an offer that is impossible to not refuse," Gantz said on Twitter, about an hour after Netanyahu issued a proposal to form "a broad unity government" with his religious allies to counter "growing" security threats.

Gantz said his party will wait for Netanyahu's mandate to form a governing coalition to expire on Oct. 23.

"We will start serious negotiations on forming a liberal unity government that will lead to a change and return hope to Israeli citizens," he wrote.

Blue and White issued a separate statement, formally rejecting the offer and saying Netanyahu's aim is "not unity but immunity." Netanyahu is a suspect in at least three criminal cases of corruption.

"He (Netanyahu) is unwilling to acknowledge that most Israelis voted for a liberal unity government without extremists," the centrist party said, referring to Netanyahu's pro-settler and ultra-Orthodox partners.

The party called on Netanyahu to return the mandate to the president and enable Gantz "to lead the formation of a government that will fix the security and economic problems the current government has created."

Israel's political system has been in a deadlock since the parliamentary election on Sept. 17, where both Netanyahu's Likud party and Gantz's Blue and White did not win enough votes to form a government.

Gantz, Israel's former military chief, and his Blue and White party won 33 seats in the 120-seat parliament. Netanyahu's Likud won 32.

The results threaten to end the decades-long dominance of Netanyahu over Israeli politics.

It was the second time in five months that Israelis had cast their ballots after the elections in April failed to bring a government.

If Blue and White also will fail to form a government, it might lead to third do-over elections.