But the prestige of a White House invitation and the chance to air grievances outweighed the misgivings.
"We will lay down our fears and anxieties ... and express the really urgent need of American support," said Deputy Prime Minister Nabil Shaath.
Abbas, widely known as Abu Mazen, flew to Washington via Jordan. He meets Bush on Thursday, part of a three-day trip to the US capital where he will speak to congressmen, Jewish and Arab-American leaders, and senior government officials.
"We have many demands concerning the current situation, and we hope that they will respond to these political and economic demands," Abbas said just before boarding a Jordanian helicopter.
Road map to peace
Abbas said he would also ask the US to push ahead with the internationally backed road map peace plan, which calls for the establishment of a Palestinian state.
Israel, the Palestinians and the United States are hoping Israel's plan to withdraw this summer from the Gaza Strip and four West Bank settlements will jump-start peace talks that have been stalled due to nearly five years of fighting.
Abbas (C) headed for Washington
for talks with President Bush
Palestinians fear Israel will use the Gaza withdrawal as an excuse to strengthen its hold on the West Bank, said Rafiq Husseini, Abbas' chief of staff. "The president wants assurances that the Gaza pullout will not be Gaza first and last," Husseini said.
Urging his people to end their uprising against Israeli occupation, Abbas was elected in January - after the November death of Yasser Arafat - on promises he would bring security, reform and an easing of the harsh burdens of Israeli occupation. But Abbas has yet to deliver.
Strength in Hamas
White House support could bolster the Palestinian position in peace talks, and more immediately, strengthen Abbas' stature ahead of a crucial parliamentary election set for mid-July.
Hamas is challenging Abbas' Fatah movement in the 17 July vote and is gaining support among Palestinians.
Tired of corruption and deadlock on the path to independence, Palestinians brought Hamas to power in a third of the municipalities up for grabs in recent elections.
"Abu Mazen wants to see ... our streets without armed people and he is taking actions towards that. But it cannot happen in one day or one afternoon"
The group is expected to make a strong showing in parliamentary balloting scheduled for July.
The US and Israel have called on Abbas to disarm Hamas and other fighter groups, an important Palestinian obligation under the road map. Abbas has refused to do so, citing fears of civil war.
Instead, Abbas negotiated a truce with the fighters three months ago, but Hamas is threatening to back out of the deal, accusing the Palestinian leader of working to delay the parliamentary vote out of fears Fatah will not fare well.
Abbas' refusal to crush the fighters is one of the main reasons the United States has been reluctant to give the Palestinians full financial and political support.
"Abu Mazen wants to see ... our streets without armed people and he is taking actions towards that. But it cannot happen in one day or one afternoon," Husseini said.
Freeze settlement expansion
In his talks with Bush, Abbas is also expected to demand intensified US pressure on Israel to freeze Jewish settlement expansion in the West Bank, a basic Israeli obligation under the road map.
Abbas is deeply concerned about an Israeli plan to build more than 3500 new homes in Maaleh Adumim, the West Bank's largest settlement.
The construction, if completed, would link the settlement to traditionally Arab east Jerusalem - cutting it off from the rest of the West Bank - and in effect destroying Palestinian dreams of making the city the capital of a future state.
Bush publicly criticised the Maaleh Adumim construction plan during a news conference with Sharon last month. But the Israeli leader vowed to push ahead, saying it is in line with an Israeli plan to hold on to chunks of the West Bank. Abbas is sure to raise the issue with Bush.
To ensure a smooth takeover of the Gaza Strip after the pullout, the Palestinians are seeking US aid to help boost their ailing economy, and rehabilitate their run-down security forces.
This year, the US Congress approved an additional $200 million in Palestinian aid, on top of $75 million approved earlier.
"The signals from Congress about aid are laden with restrictions and preconditions and do not reflect the kind of open American support we need to get through these difficult times"
Deputy prime minister
The initiative was passed after Bush, in his February State of the Union address, said he would ask Congress to support Palestinian political, economic and security reforms. But the Palestinians complain the fine print in the aid package puts unnecessary restrictions on their use of the money.
"The aid is not really coming forth," Shaath said. "The signals from Congress about aid are laden with restrictions and preconditions and do not reflect the kind of open American support we need to get through these difficult times."