As President Bush prepares to roll out his Mideast peace blueprint, members of Congress and Palestinian leaders are already expressing doubts about its core goal — provisional Palestinian statehood.

``A state is a state, and you cannot be provisionally pregnant, and you cannot have a provisional state,'' Palestinian Cabinet Minister Nabil Shaath said Sunday.

White House officials said they tentatively planned the address for Monday afternoon, but were waiting for Bush to make a final decision. They also cautioned that events on the ground could again force a change.

A senior White House official reaffirmed Sunday that Bush would outline a step-by-step proposal for establishment of a Palestinian state contingent on democratic reforms. The plan would create the state within provisional borders late this year or early next year, provided that enough measurable progress has been made in reforming the Palestinian Authority and stemming terrorism.

The thorniest issues — such as final borders, the control of Jerusalem and the return of refugees — would be left to negotiations between Israel and the provisional state.

Bush delayed an announcement last week after two suicide bombings in Jerusalem killed 26 Israelis and the Israeli army began seizing Palestinian territory in the West Bank.

Ahead of the official announcement, influential lawmakers and a Palestinian official challenged the administration's proposal.

Shaath said his people would greet Bush's proposal for interim status ``positively,'' but he was skeptical about its central provision.

``There is no such a thing as a provisional state,'' he said on Fox News Sunday.

Still, Shaath said he was eager for the United States to lay out a peace plan soon. ``The important thing is to have the United States involved with the international community because we cannot do it on our own with the Israelis. We need a third party, and there's no better than the Americans,'' he said.

``I don't know what a provisional state means,'' Sen. Joseph Lieberman, D-Conn., said on CBS' Face the Nation. ``Either you're a state or not a state.''

What's needed is a permanent Palestinian state, Lieberman said, and the way to start is for Bush to send Secretary of State Colin Powell back to the region and have him bring the parties together around the plan offered by Saudi Arabia — Arab peace with Israel in exchange for a Palestinian state on land Israel won in the 1967 war.

``It's important that the president get back on the field here,'' Lieberman said. ``The problem here is that this is going nowhere.'' He proposed substantial U.S. economic aid to Palestinians. He also would allow more Palestinians into America as part of an effort to improve ties and separate them from the culture of suicide bombing.

Sen. Richard Shelby, R-Ala., called the idea of an interim state ``a dicey proposition right now. I don't know how you can create a Palestinian state at the moment with all of the violence that's going on, all of the terrorist attacks,'' he told ABC's This Week.

Israeli Defense Minister Benjamin Ben-Eliezer said ``the offer of President Bush will be welcomed if this will be under the feeling that all of the terror activities is somehow calmed, or at least someone (does) something in order to bring it lower than it is right now.''

Israeli Foreign Minister Shimon Peres said he would embrace an interim-state proposal. ``I think the whole region is awaiting the speech of the president. As a matter of fact, things are being (delayed) because there is this expectation for the announcement by the president,'' he said.

Several of those interviewed Sunday expressed growing skepticism about Yasser Arafat's ability to lead the Palestinians.

``I think he's at a point where he has lost control,'' Lieberman said. ``It's time for a change.''

Shaath said Arafat is the elected leader of the Palestinians and will face elections again in January.

Sen. John Kerry, D-Mass., accused the administration of a ``catastrophic'' mismanagement of the Mideast crisis by engaging only fitfully there. ``There is no continuity, there is no fundamental plan,'' he said.

``They sent mixed signals to every side, if any signals at all,'' Kerry said on NBC's Meet the Press. ``And in the end, I think they have contributed significantly to their own dilemma and to the dilemma of the Middle East today as a result of that.''