Political sources said Sharon could not overcome right-wing resistance in his coalition to ceding the 17 small isolated Jewish enclaves in Gaza unless Israel could cement its hold on larger West Bank blocks, seen as strategically vital.
Israeli Prime Minister Ariel Sharon says his "disengagement plan" aims to defuse the conflict. Palestinians say it would strip them of land they seek for a viable state under the US-backed "road map" for peace.
Senior US envoys on Friday held a second day of talks with aides to Sharon to pin down what he has in mind. Washington supports Israeli withdrawals from occupied territory, but is keen not to see the road map for a negotiated peace eclipsed.
Israeli Foreign Minister Silvan Shalom said after seeing the envoys President George Bush's administration appeared to be warming to Sharon's plan after considerable skepticism.
He said Sharon intended to take no action without firm US backing.
The political sources said Sharon wanted to annex three large settlement clusters due to be taken in by the 'security-wall' Israel is erecting in the West Bank.
"For us it is a question of getting the Americans to accept that certain West Bank settlement blocs must be part of Israel in the future, as well as neighbourhoods of Jerusalem that are integral Jewish parts of Jerusalem, not settlements on occupied land as the Palestinian calls them," a senior source said.
Israel captured the West Bank and Gaza Strip in the 1967 Middle East war. It later annexed Arab East Jerusalem in a step not recognized internationally and settlements have proliferated around it since, all but cutting the West Bank in two.
Palestinian officials say Sharon wants to reduce any future Palestinian state to a weak, fragmented entity.