Washington has opposed his planned unilateral moves, Jewish settlers in the occupied territories have accused him of betrayal and Palestinians reject his "threatening" language.
The United States "would oppose any unilateral steps that block the road towards negotiations under the road map that leads to the two state vision," said White House spokesman Scott McClellan on Friday.
He was reacting to Sharon's proposal to implement his own "disengagement plan" should the Palestinians not meet their commitments under the US-backed road map peace plan in the coming months.
US officials believe "that a settlement must be negotiated and we would oppose any Israeli effort to impose a settlement," McClellan said.
He welcomed, however, Sharon's stated commitment to move forward on the road map, an internationally-drafted plan which aims to bring about a separate Palestinian state alongside Israel in 2005.
An armed settler in Migron, which
is marked for possible evacuation
"Unilateral steps can help the road map move forward ......... Israeli actions to remove outposts and settlements are part of the road map," McClellan said.
On Thursday, Sharon said Israel wants "to speedily advance implementation of the roadmap towards a quiet and genuine peace".
But he warned he would take "the unilateral security step of disengagement" if Palestinian Prime Minister Ahmed Quraya did not prevent Palestinian groups attacking Israel.
The hawkish Sharon also said his government "will greatly accelerate" the construction of its controversial apartheid wall. Washington has called the barrier's route, that often juts deep into the West Bank, a "problem," while Palestinians accuse Israel of outright land appropriation that pre-empts their future state's borders.
Israel's 320,000-strong settler community was outraged by the threat to their homes in the West Bank and Gaza Strip should Sharon carry out his "disengagement plan".
"The relocation of settlements will be made first and foremost in order to draw the most efficient security line possible, thereby creating this disengagement between Israel and the Palestinians," Sharon said.
"Settlements which will be relocated are those which will not be included in the territory of the State of Israel in the framework of any future permanent agreement."
The president of the Settlers' Council, Bensi Lieberman, vowed to oppose any forced evacuations.
Meanwhile, Palestinians deplored Sharon's "threatening" tone.
"I am disappointed that he is threatening the Palestinians," Quraya said as he stressed his readiness to negotiate with Sharon on the basis of the road map.