Sharon sent the dismissal notices on Friday to Transport Minister Avigdor Lieberman and Tourism Minister Benny Elon of the National Union Party after they failed to answer a summons to his office.
They would take effect in 48 hours, before the crucial Cabinet session on Sunday when a vote will take place over the pullout of occupation troops from the Gaza Strip.
Sharon is likely to replace them with ministers able to ensure him a majority within his Cabinet in favour of his controversial plan.
Sharon's plan includes trading 21 smaller Jewish settlements in the Gaza Strip for control of the main settlement blocs in the occupied West Bank where most of the 230,000 settlers live.
Only 7,500 settlers live in the Gaza Strip blocs.
Jewish settlements are illegal under international law, a stance not recognised by Israel.
The Jewish settlements are illegal
under international law
At present 11 ministers approve the plan while 12 are opposed.
Sharon will create a one-vote majority by firing Lieberman and Elon. Another pro-settler faction, the National Religious Party, has threatened to quit if Sharon dismissed the National Union.
The finance minister and Sharon's chief rival within the right-wing Likud party, Benjamin Netanyahu, has been leading opposition to the plan within the government.
A Sharon ally, Immigration Absorption Minister Tzipi Livni, is floating a proposal which would see the Cabinet vote on the overall principle of Sharon's "disengagement plan" but include a clause requiring another vote before any Jewish settlements are evacuated.
Sharon has voiced confidence he will garner a majority within his cabinet when he puts the plan to ministers, a week after he was forced to postpone a vote after failing to persuade enough members to come onside.
Sharon suffered a major embarrassment a month ago when a referendum among members of his Likud party rejected the plan.
Throughout Thursday Cabinet ministers tried to work out a compromise to prevent a coalition crisis, but Sharon was adamant.
"I intend to honour my commitment to bring the decision to the Cabinet this Sunday," he said.
Jewish settlers in the Gaza Strip
once saw Sharon as their champion
Lawmaker Yossi Sarid of the opposition Yahad Party ridiculed the suggested compromise, which would postpone voting on settlement evacuations for many more months.
"It's a plan without a plan, disengagement without disengagement ... a meatball with no meat, chicken soup without chicken, a concert without music," Sarid scoffed.
The sacking of the two ministers from the hard-right National Union is likely to leave him exposed to defeat when the plan is later put to parliament, with the main opposition Labour party split over whether to come to his rescue.
Labour leader Shimon Peres said he would not enter a new coalition government if Sharon's original proposal were compromised in a deal with the ministerial skeptics.
Asked by Israeli television whether he would join the government if Livni's compromise was accepted, Peres said: "No. Because it's not a compromise, it's a rejection [of the plan]."