Israel's prime minister has warned his Likud party that if it rejects his Gaza pull-out plan, it would give a huge victory to Palestinian militants.
Sharon's plans render some West Bank settlements permanent
Ariel Sharon has been campaigning to get party members to support the plan in a referendum on Sunday.
He told a series of interviewers his mind was made up and he would not even contemplate losing the vote.
Latest opinion polls suggest a narrow majority of Likud members are opposed to the so-called disengagement plan.
The plan includes a unilateral withdrawal from Gaza and parts of the West Bank, but the permanent retention of several large settlements in the West Bank.
A survey of 583 Likud members in the daily Yediot Aharonot newspaper found 47% against and 39% in favour of Mr Sharon's strategy. Fourteen percent were undecided, with no margin of error given.
"You cannot be for me but against the plan I am spearheading. Whoever believes in me must vote for the disengagement plan," he told Israel's Army Radio.
"Otherwise it will be a victory for [Palestinian leader Yasser] Arafat and [the militant group] Hamas and will ultimately bring about Likud's downfall," he added.
But Mr Sharon stopped short of saying he would quit if Likud's 200,000 members reject the plan on Sunday.
"I don't even want to think of another situation," he replied when asked what he would do if he lost.
Mr Sharon insists that his plan will bolster Israeli security, but many settler groups and their supporters disagree, portraying it as handing a victory to militant groups.
Other polls of Likud members on Thursday indicated declining support for Mr Sharon's plans.
Gaza settlers have vociferously rejected Sharon's plans
Support for Mr Sharon has dropped from 54% two weeks ago and 49% last week, the Associated Press news agency reported.
In the Ma'ariv daily, a poll found 45% of Likud respondents oppose his plans and 42% support them, with 13% undecided.
The Sharon plan gained controversial backing from US President George W Bush earlier in April, who said it was "unrealistic" for Israelis to leave some population centres on occupied land.
International law views the settlements as illegal and past peace accords stipulated that nothing should be done to prejudice final status negotiations with the Palestinian side that would decide their fate.