* Obama has blunt tone
* Keeps pressure on Israel
* Stresses his own Muslim roots
WASHINGTON, June 4 (Reuters) - U.S. President Barack Obama had a blunt, "tough-love" message for Arabs and Israelis that thrust him deeper into Middle East peacemaking -- a tangled web that bedeviled his predecessors and carries risks for him.
Quoting a Koran passage to "speak always the truth," Obama set aside diplomatic niceties in demanding Israel stop building Jewish West Bank settlements that antagonize Palestinians, for Palestinians to work for peace and accept Israel's right to exist and for Palestinian militants to halt violence.
"We cannot impose peace," Obama said on Thursday in a speech in Cairo to the world's Muslims. "But privately, many Muslims recognize that Israel will not go away. Likewise, many Israelis recognize the need for a Palestinian state. It is time for us to act on what everyone knows to be true."
His foray into the Middle East comes far earlier in his presidency than that of his predecessors, Bill Clinton and George W. Bush, who waited until late in their terms to make a major push and found themselves disappointed at the outcome.
Shibley Telhami, a Middle East expert at the Brookings Institution in Washington, said taking the initiative on Middle East peace this early means Obama's ability to deliver will become a test of his credibility.
"This administration three years from now when we're in the middle of an election campaign will in part be measured on the extent to which it brings Arabs and Israelis closer to a two-state solution," he said.
The president, who is a Christian but whose Kenyan father came from a family that includes generations of Muslims, stressed his Muslim roots in a way that he never did during his presidential campaign last year, when it might have been seen as a political liability.
That may have helped him in delivering a speech which Democratic Senator John Kerry, chairman of the Senate Foreign Relations Committee, called a blunt, honest address that was critical to signaling "a new era of understanding with Muslim communities worldwide."
'CHANGED THE CLIMATE'
"He said things that if previous presidents had said them, it wouldn't have mattered, but because he is who he is, it changed the climate in which he said them, made it more meaningful," said Ron Kaufman, who was political adviser to former President George H.W. Bush.
"The fact that a Barack Hussein Obama said these things, he can say them in a way that the moderate Muslims would listen," Kaufman said.
While direct and frank, Obama struck an empathetic tone with Muslims in seeking what he called a "new beginning" with them, trying to move beyond tensions left by the Bush administration's war in Iraq.
A former U.S. ambassador to Israel, Martin Indyk of the Saban Center for Middle East policy, said Obama presented "a dramatic and persuasive American manifesto for a new relationship with the Muslim world."
Obama's demand for Israel to freeze settlements represented a challenge for Israeli Prime Minister Benjamin Netanyahu, who has defiantly resisted taking that step, and raises the possibility of frictions with pro-Israeli members of the U.S. Congress, many from Obama's own Democratic Party.
Even before his speech, some U.S. lawmakers were signaling concerns.
Democratic Representative Anthony Weiner said on Wednesday Obama needed to be "careful not to cross the line where it sounds like we are exerting the overwhelming pressure that we have at our disposal on our rather isolated ally."
History shows tangling with Israel can at times prove costly for U.S. presidents. George H.W. Bush, president from 1989 to 1993, angered Israel and its U.S. backers by saying he would not support new money for Israel to use for settlements.
He has since told former aides he believed this issue was one reason he lost his 1992 re-election bid -- because he lost a lot of Jewish support.
James Zogby, president of the Arab-American Institute, said however that "there are very important leaders in Congress in the Jewish community who clearly understand that this path being pursued by Israel is not helpful and is more than not helpful, it is destructive."
"This is a battle he can win," Zogby said of Obama.
Given that Middle East peace has been an elusive goal of every president of the past 50 years, it would come as a surprise to most Americans if Obama were to succeed in bringing Arabs and Israelis together.
A USA Today/Gallup poll conducted late last month found that only 32 percent of Americans believed there would come a time when the two sides would be able to settle their differences and live in peace.
And 66 percent doubted it would happen.
Additional reporting by Susan Cornwell, Editing by Howard Goller
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