The speaker of the Israeli parliament will formally notify lawmakers Monday of the opposition's announcement of a coalition to unseat veteran premier Benjamin Netanyahu, his office said.

The notification will set in motion preparations for a confidence vote in the new government, which will now likely be held on Wednesday or the following Monday, Israeli media said.

The late Friday announcement by speaker Yariv Levin, a close Netanyahu ally, allays fears their right-wing Likud party could find procedural ways to block the formation of the motley coalition that would end Netanyahu's 12 consecutive years in office.

On paper, the coalition announced by opposition leader Yair Lapid just minutes before a midnight Wednesday deadline, should command a slender majority in the confidence vote.

But all eyes will be on potential defections from the disparate alliance which is united only by shared hostility to Netanyahu.

Under the agreement, Naftali Bennett of the religious nationalist Yamina party would be premier for two years, to be replaced by the centrist Lapid in 2023.

With possible jail time hanging over him in his ongoing trial on corruption charges, Netanyahu is not expected to give up without a fight.

His supporters have been working hard to win defections from lawmakers from Bennett's own Yamina party uncomfortable with their leader's alliance with Jewish leftists and Arab conservatives.

Demonstrations orchestrated by Netanyahu supporters have been held outside the home of Yamina lawmaker Nir Orbach, who has warned Bennett he may not support him in the confidence vote.

Were Orbach to vote against the deal without resigning from the party, the coalition would not have a majority.

A Friday post on Netanyahu's Facebook page said that "those who were elected on right-wing votes have to do the right thing -- to form a good, strong right-wing government".

Should last-minute defections scupper the alliance, Israel would likely have to return to the polls for its fifth election in just over two years.