Finance Minister Benjamin Netanyahu, Foreign Minister Silvan Shalom and Education Minister Limor Livnat, heavyweights in the right-wing Likud, refused on Monday to campaign for the plan, which they have only reluctantly backed.
A confidant predicted that Sharon, struggling to halt erosion in support for his unilateral "disengagement" proposal ahead of next Sunday's Likud referendum, would exact "political revenge" against those who turned him down.
"Sharon doesn't forget," the source said.
Polls indicate approval of Sharon's plan, which calls for uprooting all Jewish settlements in Gaza and four of 120 in the West Bank, is far from guaranteed by the traditionally pro-settler Likud.
A survey on Friday showed 49% of the party's 200,000 members in favour and 39.5% against.
Defeat in his own party would be a major blow to Sharon. But he has already signalled he will present the plan to parliament - where his chances of success are greater - even if he loses.
Shalom is refusing to campaign
for the disengagement plan
Sharon says a Gaza withdrawal will improve Israel's security after three and a half years of fighting with Palestinians. But many in the Likud oppose ceding any land captured in the 1967 war and have branded the proposed pullout a "reward for terror".
Palestinians see Sharon's plan as a ruse to annex large swathes of West Bank territory they want for a state.
Seeking to rally support among hardliners, Sharon resorted to tough language at memorial day ceremonies for Israelis killed in decades of Middle East conflict. "As long as our enemies use terror we will exact a heavy... price for it," he said.
In response to Sharon's plea, Netanyahu, his strongest rival, was quoted as telling him on Sunday: "I have done more than enough." Netanyahu, considered more hawkish than Sharon, is seen as his likely successor if the prime minister is toppled by brewing corruption scandals. Sharon has denied wrongdoing.
"Sharon doesn't forget"
Netanyahu, Shalom and Livnat grudgingly lent their backing to Sharon's plan after it received US President George Bush's blessing this month. But amid signs of declining support, they have rejected Sharon's appeal to promote it publicly.
"Their motives are pretty transparent: they believe, at least some of them, that Sharon is going to lose in the 2 May Likud referendum, and they don't want their names linked to the fiasco," Haaretz newspaper commentator Yossi Verter wrote.
With two far-right partners in Sharon's coalition threatening to bolt if the cabinet approves a pullout, the centre-left Labour party could opt to join a unity government.