WASHINGTON (AP) - When President Bush began his first energized pursuit of an Israeli-Palestinian peace accord just over five months ago, confidence was his constant companion. "I'm optimistic," he said over and over about the prospects for ending one of the world's longest-running disputes within little more than a year.

As the president prepares a Mideast trip this week, his second in four months, he is trading that unfailingly upbeat tone for something a bit more reserved.

It's a nod to Mideast realities.

Old barriers to peace such as distrust, violence and little movement on the most difficult issues concerning borders, Palestinian refugees and how to resolve both sides' claim to Jerusalem have run up against new ones, mainly in the form of leaders possibly too weak among their own people to cut deals.

But both the Israeli and Palestinian leaders are weak, complicating Bush's task - and his confidence.

Israeli Prime Minister Ehud Olmert is under investigation for allegations that he illicitly collected campaign cash, and has said he will resign if indicted. Palestinian President Mahmoud Abbas is constrained by the political divide between Palestinians in the West Bank where Abbas' Fatah movement is in control and in Gaza, which is governed by the Hamas militant group.

In interviews with the Israeli media Monday at the White House, Bush said his relations with Olmert were "excellent" and called the Israeli leader an "honest guy."

But in an apparent effort to separate the fate of the peace process from Olmert's own, Bush said the negotiations with the Palestinians do not depend on Olmert and singled out Israel's foreign and defense ministers as possible replacements. And, he noted that several Palestinian officials are involved in the peace talks, not just Abbas.

"I certainly think there's a coming to grips with reality," said Nathan Brown, a Mideast expert at the Carnegie Endowment for International Peace and director of George Washington University's Institute for Middle East Studies.

In November, when Bush convened nearly 50 countries in Annapolis, Md., for a Mideast peace conference that launched the first formal negotiations in years between Israelis and Palestinians, he repeatedly said a deal was doable by the time he leaves office next January.

"I wouldn't be standing here if I didn't believe that peace was possible," he said at a Rose Garden send-off for Olmert and Abbas.

Bush was just as cheerful in January before, during and after a Mideast trip. "There's a good chance for peace," he said in Israel, his first visit there as president. "When I say I'm optimistic we can get a deal done, I mean what I'm saying," Bush said in Egypt.

He kept this stance into March, despite no visible progress in the Israeli-Palestinian talks that include bimonthly meetings between Olmert and Abbas. Bush declared that the 10 months left on his self-imposed peace clock was "plenty of time." "I'm still as optimistic as I was after Annapolis," Bush said after meeting at the White House with Jordan's King Abdullah II.

The approach is classic Bush, for whom a favorite story is how the choice of an Oval Office rug with a sunburst pattern says "optimistic person comes to work" to visitors. Truth be told, it's not so uncommon for most politicians and diplomats, said Jon Alterman, head of the Middle East program at the Center for Strategic and International Studies in Washington.

"The president is optimistic because he thinks his job is to be optimistic," he said.

But Bush was less ebullient by the time Abbas visited the White House last month to plead for stepped-up U.S. involvement in the negotiations, particularly to ride herd on Israel to halt settlement activity in Palestinian areas. "I'm confident we can achieve the definition of a state," he told Abbas, somewhat flatly.

Perhaps even more significantly, Secretary of State Condoleezza Rice told an American Jewish audience a few days later that "we have a chance to reach the basic contours of a settlement by the end of the year."

As Bush was preparing for this week's trip, Rice said it was "a misperception that not that much is going on in the political negotiations." Her language was tempered, however. "I'm also a big believer that nothing is really impossible," she said in an interview aired Tuesday on CBS' "The Early Show." "It might be improbable but it's not impossible."

In the painstaking, tea-leaves world of Mideast diplomacy, Bush describing the goal as the "definition of a state" and Rice's talk of merely "a chance" for "the basic contours of a settlement" are read by experts and those in the region as a scaling back of initial hopes for a full-blown treaty. Though the White House was vague from the beginning about what it was seeking from the talks, the distinct impression was left that the envisioned final product was an end to the conflict and the definition of a Palestinian state.

Now, Palestinians are becoming increasingly suspicious that the Israelis are looking to achieve something by the end of the year that is much less than a full treaty, and that they are supported in this by Washington.

The Carnegie Endowment's Brown said this sort of disappointment is a price of Bush's high-flying original rhetoric. Though it was widely seen as overblown at the time, it still created expectations - and reduced his credibility.

"Anything less than some kind of agreement is going to be seen as failure," Brown said.

Bush's trip now seems designed as much as a ceremonial journey.

In Israel he'll participate in festivities surrounding the 60th anniversary of the Jewish state. His stop in Saudi Arabia later in the week is billed as a celebration of 75 years of formal U.S.-Saudi relations, though Bush said in a CBS News radio interview Monday he also will bring up the effect that high oil prices are having on the U.S. and global economies. But he noted that the capacity of the Saudis to raise production - and thus help lower prices - is limited.