WASHINGTON — U.S.-sponsored talks between Israel and the Palestinians begin Wednesday with a goal to fast-track a peace deal inside one year, an ambitious schedule even under the best of circumstances.

These aren't the best of circumstances.

For starters, the Palestinians have threatened to walk out just four weeks after talks begin.

A 10-month slowdown in West Bank housing construction by Israel is set to expire at the end of September, and the government is divided over whether to extend it. The Palestinians have warned they will pull out of the new round of negotiations if building resumes.

The West Bank would make up the bulk of an independent Palestinian state alongside Israel, with precise borders to be drawn at the peace table. Expansion of Jewish housing makes those borders ever more complicated.

The militant Hamas movement, opposed not only to talks but to Israel's very existence, is in firm control of the Gaza Strip. Gaza, which is also supposed to be part of a negotiated Palestinian state, has been the staging point for rocket attacks on Israel that have led to an almost complete Israeli blockade of the territory.

Neither Israeli Prime Minister Benjamin Netanyahu nor Palestinian President Mahmoud Abbas has much political elbow room at home.

The failure of past peace efforts has left both sides with rigid demands and public ambivalence about the value of a negotiated settlement.

To this cloudy horizon, President Barack Obama brings the promise of impartial brokerage and a steady hand at each man's back. Despite his popularity abroad, many Palestinians and Israelis are skeptical of Obama, and suspect the U.S. has a finger on the scale.

Face-to-face talks between Netanyahu and Abbas will be the first for the two sides in nearly two years, since talks broke down under Netanyahu's predecessor at the close of President George W. Bush's administration.

Obama aides say they know the timing for the latest talks isn't ideal, but that the risks of waiting are growing. The Israeli-Palestinian conflict is a constant source of grievance and unrest in the Muslim world; Secretary of State Hillary Rodham Clinton and Gen. David Petraeus have said the impasse frustrates other U.S. goals around the world and fuels extremism.

Aides, including Mideast mediator George J. Mitchell, are convinced that the two sides must show some progress after two years of stagnation, according to an Obama administration official who spoke on condition of anonymity because of the sensitive nature of the diplomacy. The official said there "really was no right time" to resume the talks.

The negotiations represent Obama's deepest involvement to date in an issue he promised to confront early in his administration, but his role from this point is undefined.

Asked how much time Obama will devote to mediation, officials have said that will depend on how much his authority is considered necessary at any particular point.

He is taking on one of the world's longest-running crises at a time when his popularity has slipped among American voters. According to AP-GfK polling, the country is split about evenly, with 50 percent approving of the job he is doing and 49 percent disapproving.

Mitchell did much of the preliminary work in resuming negotiations. The U.S., he told reporters when the new round of talks was announced, "will be an active and sustained participant" and have the support of allies around the world.

Leaders of Egypt and Jordan, the two Arab nations that signed peace treaties with Israel, are expected to attend the inaugural dinner in Washington.

The talks are expected to move slowly, at least at first, because of the serious issues involved: the Palestinian quest for statehood and Israel's insistence on an undivided Jerusalem as the Jewish capital.

U.S. officials say the one-year framework for the talks is not a deadline, but provides useful discipline.

Neither side may have incentive to hold to that schedule, especially if leaders think they can use the White House's support to squeeze a little more out of the other side.

President Jimmy Carter faced imminent breakdown in the negotiations at Camp David in 1978 and had to travel to the region to drive the treaty through for signing in 1979.

Success would give Obama an aura that Carter achieved back in 1979 when Israel and Egypt signed a peace treaty, the first between Israel and an Arab state.

But that aura didn't help Carter politically. A few months after the peace deal was signed, Carter lost the White House to Ronald Reagan as Iranian extremists held the U.S. Embassy captive for 444 days.

EDITOR'S NOTE — Anne Gearan covers U.S. national security policy. Barry Schweid has covered U.S. peace efforts in the Middle East since 1973.