JERUSALEM >> Prime Minister Benjamin Netanyahu announced today that he had failed to form a majority government in parliament, marking a major setback for the embattled Israeli leader that plunges the country into a new period of political uncertainty.

In a statement, Netanyahu said he had worked “tirelessly” to establish a unity government with his chief rival, former military chief Benny Gantz, but been repeatedly rebuffed. Facing a Wednesday deadline, Netanyahu said he was returning the “mandate” to President Reuven Rivlin, who will now ask Gantz to try to form a coalition.

While Netanyahu remains at the helm of his Likud party, his announcement marked the second time this year that he has been unable to form a government. With Israel’s attorney general set to decide in the coming weeks on whether to indict Netanyahu in a series of corruption cases, the longtime Israeli leader could come under heavy pressure to step aside.

In last month’s national election, Netanyahu fell short of securing a 61-seat parliamentary majority. But Rivlin gave Netanyahu the first opportunity to form a government because he had more support — 55 seats — than Gantz, who was supported by only 54.

Netanyahu had hoped to form a broad “unity” government with Gantz, who heads the centrist Blue and White party. But Netanyahu insisted that his coalition include his traditional allies, a collection of hardline and religious parties, drawing accusations from Gantz that he was not negotiating in good faith.

“Since I received the mandate, I have worked tirelessly both in public and behind the scenes to establish a broad, national unity government. That’s what the people want,” Netanyahu said in a statement.

“During the past few weeks, I made every effort to bring Benny Gantz to the negotiating table. Every effort to establish a broad national unity government, every effort to prevent another election,” he said. “To my regret, time after time he declined. He simply refused.”

In a short statement, Gantz’s Blue and White party said that “now is the time of action.”

“Blue and White is determined to form the liberal unity government, led by Benny Gantz, that the people of Israel voted for a month ago,” it said.

There is no guarantee, however, that Gantz will succeed.

He has expressed willingness to form a partnership with Likud, but not if Netanyahu continues to lead while he faces such serious legal problems. For the time being, Likud has remained steadfastly behind its leader.

Without Likud, Gantz will have a hard time securing a majority in parliament. The opposition to Netanyahu includes a diverse group of parties, ranging from Arab parties to the secular ultranationalist party Yisrael Beitenu, that are unlikely to sit together in partnership.

If Gantz fails during his 28-day window, a majority of lawmakers could try to endorse a third candidate, something that has never happened before. And if that fails, the country would be forced into the unprecedented scenario of a third election in under a year.