Acting Prime Minister Ehud Olmert briefed the U.S. last week on his plan to impose Israel's final borders with the Palestinians if efforts to restart peace talks fail, an Olmert spokesman said Sunday.

Spokesman Asaf Shariv said that an Olmert aide presented the plan in a telephone call to a U.S. official before the acting prime minister disclosed it in published interviews last week.

"They neither approved nor objected to it," Shariv said.

U.S. Embassy spokesman Stewart Tuttle said he could not confirm the report.

Shariv would not disclose who took part in the phone call. But he said Olmert would not discuss the plan with President Bush until after Israeli elections.

Backing from Washington, Israel's closest and most powerful ally, would be critical for any major initiative.

In the interviews, Olmert said he planned to withdraw from much of the West Bank and parts of Jerusalem by 2010, dismantling most of the more than 120 West Bank settlements. But Israel would retain and fortify the large settlement blocs, where the majority of the 253,000 West Bank settlers live, and maintain control of the Jordan River Valley, between Jordan and the West Bank.

It also would keep most of Jerusalem, including its disputed holy sites, which Palestinians claim as part of the capital of their future state. Olmert said he was prepared to give up some outlying Arab neighborhoods.

He said he expected to win U.S. and broader international support for the effort, which he expects to launch after Israel's March 28 elections. Polls show Olmert's Kadima Party easily winning the vote.

The U.S., the main architect of the "road map" peace plan, supports a negotiated settlement of the Israeli-Palestinian conflict, not another unilateral move like last summer's withdrawal from the Gaza Strip and four small West Bank settlements.

But the U.S. also recognizes that the political map has changed radically with Hamas militants' ascent to power in the Palestinian Authority.

Hamas, which has carried out dozens of suicide bombings against Israel, has refused to abandon its violent ideology, and rejects negotiations with Israel. The U.S., like Europe and Israel, considers the group to be a terrorist organization.

Palestinian officials reject Olmert's plan, insisting final borders between Israel and a Palestinian state must be determined by negotiations.

A senior official of the militant Palestinian Hamas group criticized it again Sunday.

"It's a unilateral separation plan," Moussa Abu Marzouk, deputy chief of Hamas' political bureau, told The Associated Press by phone from Saudi Arabia. "This cannot be accepted by any Palestinian because it violates our people's rights."

Israel is still practicing "an expansionist policy and annexing territories by force," he added.

Israel's recognition of national Palestinian rights and the return of all Palestinian refugees would create "a better chance" for making peace in the region, he said.

In Gaza City on Sunday, other Hamas officials reiterated that the incoming Hamas government remains committed to "resistance" against Israel and is not prepared to recognize the Jewish state.

In deference to international preference for a negotiated settlement, Olmert said he would only move unilaterally if long-stalled peace talks don't restart.

Palestinian Authority President Mahmoud Abbas, a member of the rival Fatah Party, has said he intends to press his agenda of restarting negotiations. But Olmert has made it clear that Israel would not negotiate with Abbas if Hamas does not change its ways.

President Bush has backed Israel's claims to keep some settlement blocs, but U.S. officials have reacted coolly to Israeli claims on the Ariel settlement bloc, deep inside the West Bank, and the Jordan River Valley.