Israeli Prime Minister Benjamin Netanyahu and his rival Benny Gantz traded blame Sunday over the failure so far of efforts to reach a unity government deal following deadlocked elections.

A new round of negotiations between Netanyahu's right-wing Likud and Gantz's centrist Blue and White broke down Sunday and the two sides appeared far from reaching a compromise.

Likud said Netanyahu would make a "last effort" to reach a deal before informing President Reuven Rivlin he is unable to form a government.

That would leave Rivlin to decide whether to ask Gantz to try to do so or call on parliament to agree on a candidate for prime minister by a vote of at least 61 out of 120 members.

Netanyahu "will make a last effort to realize the possibility of forming a government at this stage, before returning the mandate to the president," Likud said in a statement.

It called the latest round of negotiations a "big disappointment."

Blue and White accused Likud of "throwing around slogans with the sole aim of generating support in preparation for dragging Israel into another round of elections at the behest of Netanyahu."

This month's poll was the second this year, after Netanyahu failed to form a coalition following April's vote.

Rivlin tasked Netanyahu with trying to form a government Wednesday and he has 28 days to do so, with a two-week extension possible.

The deadlocked vote has threatened Netanyahu's reign as Israel's longest-serving prime minister.