Sharon's unprecedented plan for giving up Jewish enclaves on territory occupied since the 1967 war has drawn death threats and warnings of civil war while splitting the ruling Likud party and throwing the political landscape into turmoil.
In a serious challenge after parliament passed the US-backed Gaza plan on Tuesday, Sharon's chief Likud rival Finance Minister Benjamin Netanyahu and three other ministers vowed to resign in two weeks if no referendum was set.
"I will never give in to pressures and threats and not accept any ultimatums," Sharon told Haaretz newspaper. "My position on the referendum is unchanged - I am opposed because it will lead to terrible tensions and a rupture in the public."
Sharon fears that a referendum could delay the start of the withdrawal of troops and settlers from Gaza and four of the 120 settlements in the West Bank, slated to begin after another cabinet vote next March.
But the loss of Netanyahu and the others could make it hard for Sharon to avoid a leadership challenge or new elections.
Netanyahu, a former prime minister, is also hailed by markets as the architect of economic reforms.
"We still cannot rule a referendum out totally. This is politics," said one Sharon confidant.
Another option for Sharon could be to strengthen his shaky coalition by bringing in centre-left opposition Labour, whose Knesset deputies all voted in support of Sharon despite his standing for decades as bogeyman of the left.
Embracing Labour, though, could mortally wound the Likud that Sharon co-founded and deny him the party's selection for new elections. While Sharon's plan cleared parliament 67-45, the Likud vote was split to 23 for and 17 against.
Sharon's plan cleared parliament
at 67 - 45 votes
Netanyahu, who voted in favour of the pullout, said Sharon's choice between calling a referendum and forming a Labour alliance was "between a government which will bring a huge rift among the people or a Likud government which can be sustained."
Polls show that most Israelis support the plan to quit Gaza, seeing the cost in blood and money as too high for keeping 8000 Jews in fortified colonies alongside 1.3 million Palestinians.
But nationalist hardliners, who once saw Sharon as the settlers' godfather, now revile him for being ready to give up land they see as a biblical heritage to Palestinians waging a 4-year-old uprising.
Security around Sharon has been tightened amid an upsurge of fiery language last heard before Prime Minister Yitzhak Rabin was assassinated by an ultra-nationalist Jew in 1995 for signing accords with the Palestinians.
Palestinians welcome a withdrawal from any land, but fear that the pullout from Gaza would be at the expense of a stronger Israeli hold on bigger West Bank settlements, effectively denying them the state they seek in both territories.
A pillar of Sharon's plan are assurances from US President George Bush that Israel would not be expected to give up the whole West Bank under any future peace deal.