Yoram Dori, a spokesman for Labour leader Shimon Peres, said on Friday that all obstacles had been removed and that the accord would be formalised within 24 to 36 hours.
Sharon's spokesman, Asaf Shariv, said Labour would have eight ministerial posts, including two without portfolio, under the deal.
One of the posts goes to Peres who will be deputy-prime minister at the office of the prime minister, while incumbent Deputy Prime Minister Ehud Olmert would remain in his post.
The five portfolios being allocated to Labour are interior, housing and construction, infrastructure, tourism and telecommunications, according to Shariv, who said the accord would be signed on Sunday.
Sharon, short of a majority for more than six months, needed to bring Labour into government to ensure implementation of his controversial plan to pull Israeli soldiers and settlers out of Gaza in 2005.
Palestinians are against Sharon's Gaza plan as it does not comply with the internationally recognised road map to peace. Palestinians say the plan also suggests that Israel will confiscate other Palestinian territory in the West Bank on a permanent basis.