Far-right two If Israeli Prime Minister Benjamin Netanyahu accepts a ceasefire proposal presented by US President Joe Biden on Friday, Israeli ministers have vowed to resign and bring down the ruling coalition.
National Security Minister Itamar Ben-Gavir and Finance Minister Bezalel Smotrich said they were opposed to striking any deal before Hamas was destroyed.
But opposition leader Yair Lapid has pledged to back the government if Mr Netanyahu supported the plan.
The prime minister himself insisted there would be no permanent truce until Hamas's military and governing capabilities were destroyed and all hostages released.
Mr Biden's three-part proposal would begin with a six-week ceasefire in which the Israel Defense Forces (IDF) would withdraw from populated areas of Gaza. The deal would eventually lead to the release of all hostages, a permanent "cessation of hostilities" and a major reconstruction plan for Gaza.
But in a post on social media on Saturday, Mr Smotrich said he told Mr Netanyahu he would "not be part of a government that agrees to the proposed outline and ends the war without destroying Hamas and bringing back all the hostages".
Echoing his words, Mr Ben-Gvir said "the deal.. means the end of the war and the abandonment of the goal to destroy Hamas. This is a reckless deal, which constitutes a victory for terrorism and a security threat to the State of Israel".
He vowed to "dissolve the government" rather than agree to the proposal.
Mr Netanyahu's right-wing coalition holds a slim majority in parliament, relying on a host of factions, including Mr Ben-Gvir's Otzma Yehudit (Jewish Power) party - who hold six seats - and Mr Smotrich's Religious Zionism party - who hold seven seats - to maintain power.
But Yair Lapid, one of Israel's most influential opposition politicians, was quick to offer his backing to the embattled prime minister. His Yesh Atid (There is a future) party hold 24 seats.
He said Mr Netanyahu "has our safety net for a hostage deal if Ben-Gvir and Smotrich leave the government".
The row came as tens of thousands of people rallied in Tel Aviv, calling on the Israeli government to accept Mr Biden's proposed plan. They also demanded Mr Netanyahu's resignation. Scuffles broke out between protesters and police, and some demonstrators were reportedly detained.
In a joint statement on Saturday, mediators from Egypt, Qatar and the US urged both Israel and Hamas to "finalise" Mr Biden's proposed deal.
Officials said that "as mediators in the ongoing discussions to secure a ceasefire in Gaza and the release of hostages and detainees", they "call on both Hamas and Israel to finalise the agreement embodying the principles outlined by President Joe Biden".
UK Prime Minister Rishi Sunak also offered his backing to the plan, telling reporters that his government could "flood Gaza with far more aid" if Hamas accepts the ceasefire plan.
Earlier, a senior Hamas politician told the BBC it "will go for this deal" if Israel does.
But in a statement on Saturday, Mr Netanyahu's office said Israel's "conditions for ending the war have not changed".
It listed these as "the destruction of Hamas military and governing capabilities, the freeing of all hostages and ensuring that Gaza no longer poses a threat to Israel".
The statement added Israel would "continue to insist these conditions are met" before agreeing to a permanent ceasefire.
Elsewhere, fighting continued in Rafah on Saturday, with reports of Israeli air strikes on Gaza's southern city on Egypt's border.
Shelling and gunfire were also reported in Gaza City, in the north of the Palestinian territory.
More than 36,000 people have been killed in Gaza since the start of the conflict, according to the Hamas-run health ministry.
The war began on 7 October 2023 when Hamas gunmen launched an unprecedented attack on Israel, killing about 1,200 people and taking 252 back to Gaza as hostages.