The main opposition leaders, former Prime Minister Yair Lapid and former Defence Minister Benny Gantz, had agreed in principle to join a unity government following the surprise attack on Saturday by the Islamist group Hamas.

A spokesperson for Gantz's National Unity party said she was optimistic there would be "good news" the party would unite with Netanyahu to form an emergency government but would not elaborate on the terms.

A meeting between Gantz and Netanyahu was scheduled for Tuesday but was delayed to Wednesday.

The agreement by political parties that are normally deeply hostile to one another underlines the scale of the crisis following the killing by Hamas gunmen of more than 1,000 Israelis at the weekend and the capture of more than 100 others.

"An emergency unity government now!" Finance Minister Bezalel Smotrich, who represents a hard right party close to the West Bank Jewish settler movement, posted on social media.

The unprecedented scale of the Hamas assault has helped overcome bitter divisions over plans by the most far-right government in Israeli history to enact legislation that would strip the highest court of much of its power.

Israel has responded to the attack with a massive bombardment of Gaza and deployed thousands of troops around the narrow coastal enclave amid growing expectations it will launch a land invasion to destroy Hamas.

In a statement on Saturday, just hours after the attack, opposition leader Lapid said he informed the prime minister that he was willing to put political differences aside and "establish together with him a professional, limited emergency government, which will manage the difficult, complex and protracted campaign before us."

A source close to Lapid told Reuters that the offer still stood if the emergency government was "narrow and professional."