>>>WASHINGTON -- The United States and Israel are among the world's closest allies, but their leaders have had a rocky relationship over the past four years.

President Barack Obama and Israeli Prime Minister Benjamin Netanyahu have disagreed in public repeatedly on how to deal with Iran's controversial nuclear program and Jewish housing on occupied land claimed by Palestinians. That poses a challenge to the two leaders as they prepare to meet in Israel this month.

Their first major dispute began in Cairo in June 2009. In a speech to the Arab world, Obama criticized Israel's policy of building Jewish homes on West Bank land the Palestinians want for a state.

"The United States does not accept the legitimacy of continued Israeli settlements," Obama said.

Days later, Netanyahu responded by saying Israel needs to let settlers "lead normal lives" - a euphemism for building more homes.

Disagreeing on Jerusalem

In March 2010, Israel approved new housing in Palestinian-claimed East Jerusalem as Vice President Joe Biden visited the country. Biden quickly condemned the Israeli move at Obama's request, saying it undermined the trust needed to begin Israeli-Palestinian peace talks.

Netanyahu rejected that condemnation. In remarks to U.S. pro-Israel group AIPAC in Washington, he said the Jewish people have a right to build anywhere in what they consider to be their united capital.

"Everyone knows that these neighborhoods (of East Jerusalem) will be part of Israel in any peace settlement," Netanyahu said.

When the Israeli prime minister went to the White House the next day, President Obama appeared to snub him. There was no official photo of their meeting.

Aaron David Miller, vice president of the Washington-based Woodrow Wilson International Center for Scholars, said these incidents were signs of deteriorating relations.

"This is the worst relationship between an American president and an Israeli prime minister in the history of U.S.-Israel relations," Miller said. "Menachem Begin and Jimmy Carter had tensions, Yitzhak Shamir and George H.W. Bush had tensions, but they found a way to work together. Obama and Netanyahu have not."

Failed peace effort

Obama brought Netanyahu and Palestinian President Mahmoud Abbas to the White House for peace talks in September 2010.

But the initiative collapsed as Netanyahu ended a 10-month freeze on West Bank housing starts and Abbas protested by refusing further talks.

Obama tried to revive the process in May 2011. In a speech at the State Department, he publicly endorsed a longstanding Palestinian demand.

"The borders of Israel and Palestine should be based on the 1967 lines with mutually agreed swaps, so that secure and recognized borders are established for both states," he said.

A day later, Netanyahu challenged the president's position during a face-to-face White House meeting in front of the cameras.

"While Israel is prepared to make generous compromises for peace, it cannot go back to the 1967 lines because these lines are indefensible," he said.

Election interference?

More tension surfaced in July 2012, when Netanyahu warmly greeted visiting Republican presidential candidate Mitt Romney, a critic of Obama's policy on Israel. Obama supporters accused the Israeli leader of taking sides in the U.S. election.

Supporters of Netanyahu made the same accusation against the U.S. president prior to Israel's election in January. Earlier that month, American political commentator Jeffrey Goldberg had quoted Obama as saying "Israel doesn't know what its own best interests are."

After Netanyahu was asked to form the next Israeli government, Obama agreed to make his first presidential visit to Israel.

Motives for cooperation

Miller said the U.S. president wants to see if the Israeli prime minister can work with him to resolve regional problems.

"Obama stands to be the American president on whose watch Iran either gets the (nuclear) bomb or has to be bombed (by him), and he also stands to be the American president on whose watch the (Israeli-Palestinian) two-state solution expires," he said. "Prime Minister Netanyahu was weakened by the Israeli election and understands that he has same two problems."

Both leaders accuse Iran of trying to develop nuclear weapons under cover of a civilian energy program and refuse to rule out military strikes to stop it. But, Obama has said more time is needed for sanctions and diplomacy, while Netanyahu has demanded the setting of a deadline for action.

Enduring partnership

Miller said those differences have not weakened the basis of the U.S.-Israel alliance.

"It does not really matter what happens at the top (of the leaderships)," Miller said. "The security cooperation continues to improve, the institutional ties deepen. The public dimension also is important, with the American Jewish community playing a critical role in orchestrating (U.S. support for Israel). But, the foundation of that support lies in non-Jewish elites and the general public."

While in Jerusalem, Obama is expected to dine with Netanyahu under the media spotlight. The world will be watching to see if they can move closer to achieving peace in the Middle East.