Bush has a frank exchange with Sharon, writes Patrick Smyth, Washington Correspondent.
As the US Secretary of State, Mr Colin Powell, packed his bags for his trip to Europe and then the Middle East, the US administration over the weekend hardened its demands on all the sides.
President Bush made clear that his call on Thursday on the Israelis was for an immediate withdrawal from recently occupied Palestinian cities, and senior officials were saying that Mr Powell is travelling with the expectation he can co-opt the region's Arab leaders to engage more directly in the peace process.
Speaking to journalists at Crawford, Texas, on Saturday, during a break in his meeting with the British Prime Minister, Mr Blair, Mr Bush insisted that Israel must "withdraw without delay" before ringing the Israeli Prime Minister, Mr Ariel Sharon, with the same message. A senior administration official described the conversation as "pretty brutal".
Mr Blair endorsed the demand, insisting that he believed Israel would heed the advice of the country's two best friends in the world, the US and Britain.
Mr Powell, speaking at the State Department yesterday before his departure, said that he would meet the Palestinian President, Mr Yasser Arafat, "if circumstances permit" but he warned that access and security problems might prevent a meeting.
He is due to reach Jerusalem on Thursday after a series of meetings in Europe and then a series of meetings around the region starting in Morocco.
Officials say Mr Powell hopes to persuade Morocco's Prince Mohammed, Saudi Arabia's Crown Prince Fahd, Jordan's King Abdullah and Egypt's President Mubarak to help craft an Arab denunciation of suicide bombing as a tactic and, in a reflection of US frustration with the Palestinian leader, to get directly involved in putting pressure on Mr Arafat to crack down on terrorism.
The former National Security Adviser, Mr Zbigniew Brzezinski, suggested yesterday that even a limited statement from the Arab leadership condemning suicide bombings but recognising the right of the Palestinians to resist occupation could provide an opening.
And, crucially, Mr Powell has been more explicit about the need for talks to go beyond security issues to engage in the politics of a final settlement. "We are prepared to talk about final status and the steps for getting there," he said.
"We are prepared to talk about a comprehensive settlement and the way stations."
"Tenet and Mitchell [peace proposals] are all for one purpose, and that is getting to negotiations, getting to a process that will lead to a settlement. "The political dimension is key, and we have to bring it as far forward and as early into the process as is possible."
Arab leaders will want to see details before they sign on - what form new negotiations would take, who would particpate in the talks and what issues would be on the table.
"My understanding is that everybody needs to play their part," an Arab diplomat told The New York Times.
"The United States also has a responsibility to lay out what their vision is so we can help them achieve it, so we can know what the game plan is."
On Iraq, Mr Blair carefully measured his words to show support for Mr Bush without endorsing potential military action.
"Any sensible person looking at the position of Saddam Hussein and asking the question 'would the region, the world and, not least, the ordinary Iraqi people, be better off without the regime of Saddam Hussein?' ...the only answer anyone could give to that question would be 'yes', Mr Blair said.
But neither leader elaborated on how that could be accomplished. "How we deal with it, that's an matter we discuss," Mr Blair said.