Hours before the president and Mrs. Bush were to fly to Tel Aviv, White House officials were cautioning against any expectations for major breakthroughs in the quest for peace in the Middle East.

Spokeswoman Dana Perino said the Israelis and Palestinians have complex issues to resolve, adding that if agreements were easily reached, the situation would have been solved long ago. She said President Bush cannot do the two parties' work for them, but noted that negotiations have yielded what she termed "halting" progress.

In an interview with CBS Radio, Mr. Bush said he does not expect to encounter "a perfect political environment", but said he hopes to see Israelis and Palestinians make progress on defining a Palestinian state.

"It is the vision that is going to make it clear for the Palestinians to see a way forward," said President Bush. "I would not assume that, if this vision gets defined, that people in the Gaza will not say, 'We are sick of the life we have now.' And that is why it is going to be so important to convince the Palestinians and the Israelis to define that state."

Shortly after arrival, Mr. Bush is to meet with his Israeli counterpart as well as Prime Minister Ehud Olmert in Jerusalem. Thursday, the president addresses the Israeli Knesset, followed by a reception in honor of Israel's 60-year anniversary.

Friday, Mr. Bush travels to Saudi Arabia, where the president says a tightening of the world's oil supply is sure to arise in talks with King Abdullah.

"When you analyze the capacity for countries to put oil on the market, it is just not like it used to be," Mr. Bush said. "The demand for oil is so high relative to supply these days that there just is not a lot of excess [production] capacity."

The final stop will be Egypt, where Mr. Bush will meet with President Hosni Mubarak, as well as the leaders of Afghanistan and the Palestinian Authority. White House officials say they would like to include Lebanon's prime minister in the discussions in Egypt, but that nothing has been finalized.

President Bush is not the first U.S. leader to devote significant efforts to Middle East peace initiatives in the latter years of his administration. His predecessor, Bill Clinton, brought Israeli and Palestinian officials together in Maryland in 1998 to negotiate an agreement implementing a previous accord on the future of the Gaza Strip and the West Bank.

Mr. Bush's efforts have taken various forms, beginning with the "road map" for peace crafted in 2002, which aimed to end the conflict between Israelis and Palestinians and lay the groundwork for an eventual Palestinian state.