Abbas, who will ask Bush at the White House on Friday to apply pressure on Israeli Prime Minister Ariel Sharon (news - web sites), also challenged Congress' traditional unqualified support for Israel.
A Palestinian official close to Abbas said he had told the leaders in a closed session that "if Congress continues blindly to support Israel without considering Palestinian concerns, then President Bush's vision will not be attainable."
Still, Abbas pledged again to pursue reform within the Palestinian movement and to implement the U.S.-backed road map for peace with Israel that envisions a Palestinian state by 2005.
Sen. Joseph R. Biden Jr. of Delaware, the senior Democrat on the Senate Foreign Relations Committee, told reporters afterward he was impressed with Abbas' "sense of determination and optimism."
The committee chairman, Sen. Richard G. Lugar, R-Ind., said he had promised to help in securing more U.S. assistance for the Palestinians. This year's aid exceeds $200 million.
In a brief exchange with reporters, Abbas said the administration should tell Israel "it is key" that all Palestinian prisoners be released from Israeli jails.
At the same time, Mohammed Dahlan, the Palestinian security chief, held an unannounced meeting with Condoleezza Rice (news - web sites), Bush's national security assistant.
Dahlan told her the administration should set a timetable for Israel to implement the U.S.-backed road map for peacemaking. He also called for the lifting of Israel's confinement of Palestinian leader Yasser Arafat (news - web sites) to his headquarters in Ramallah on the West Bank, sources close to Dahlan said.
Rice later called on Abbas at his hotel.
Secretary of State Colin Powell (news - web sites), meanwhile, told the Lebanese Broadcast Corp. and the London-based Arab newspaper Al-Hayat that meeting the goal of a Palestinian state by 2005 would be difficult but could be achieved.
"I think it is still possible to keep going and then speed things up as more confidence is gained," Powell said.
On another issue, Powell said Hamas and Islamic Jihad, which agreed last month to a cease-fire in killing Israelis, had retained the capacity to conduct terror attacks.
But, significantly, Powell did not insist that the Palestinian organizations be broken up. He said they had to eliminate "all capability to conduct terrorist activity" if they wanted to play a role in the future.
Elaborating later at a news conference, Powell said Hamas "has a social wing that does good things." He said Hamas would be a different organization if it gave up its weapons and abandoned terrorism.
Abbas also met with about 50 leaders of American Jewish groups at a midtown hotel.
Michael Bohnen, chairman of the Jewish Council for Public Affairs, said it was an encouraging and very positive 75-minute session.
Abbas promised to deal firmly with any lawbreakers, Bohnen said.
Asked when he might move to dismantle terror groups, the Palestinian prime minister replied "it cannot be done overnight," Bohnen said.
Slow to get started on Mideast peacemaking but now resolved to see it through, Bush faces appeals from Palestinian and Israeli leaders to pressure the other side on core issues.
Bush's goals are clear: a Palestinian state by 2005 and an end to terror attacks on Israel. The question is whether he can resist urgings to speed up his deliberate pace.
"I am sure that both sides want to see progress come faster," Powell said Wednesday. "But you can't go faster than circumstances permit."
Besides, Powell said, "progress has been made."
Abbas is urging the president to put the heat on Israel to clear out of the West Bank to make way for the Palestinian state. He especially wants Jewish settlements dismantled.
Palestinian information minister Nabil Amr suggested Wednesday the Palestinian Parliament might oust Abbas if he doesn't leave the White House with substantial Israeli commitments.
Sharon, who calls on Bush next Tuesday, has tough demands, as well. At the top of his list is that Abbas confront terror groups and immediately start uprooting them.
Martin Indyk, a former U.S. ambassador to Israel, said that "the road map is pretty much stuck at the moment. It is barely moving." And, Indyk said in a telephone interview from Jerusalem, the view in the region was that Bush had "basically stopped trying to move the ball at all."
Specifically, Indyk said U.S. monitors have stopped their oversight of the two sides, the Palestinians were not dismantling or disarming terror groups and Israel was barely moving on removal of settlement outposts on the West Bank.
"There is not much happening, and the United States is not doing much to make that happen," Indyk said.
However, he said he assumed that was going to change and that Bush would try to inject energy into the process.
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Associated Press Writer Lara Sukhtian contributed to this article.
