The White House has given its tacit backing to Israel's military operation against Hamas and the Gaza Strip, a flare-up that is threatening to seriously complicate any peace efforts envisaged by the incoming administration of President-elect Barack Obama.

"The United States understands that Israel needs to take actions to defend itself," said White House spokesman Gordon Johndroe.

"In order for the violence to stop, Hamas must stop firing rockets into Israel and agree to respect a sustainable and durable ceasefire."

It is an attitude that is very similar to the one adopted by the Bush administration during the 2006 war between Israel and Hezbollah in Lebanon - calling for a sustainable cease-fire and a lasting peace rather than pressuring Israel to immediately halt a military operation that was killing civilians.

Short of a dramatic development, observers expect no shift in this position - or the administration's support for Israel - during the remaining three weeks of President George W Bush's term in office.

Mr Bush has not made any public comments so far, and neither has his secretary of state, Condoleezza Rice. But the state department has been keen to stress diplomatic efforts are underway to bring the crisis under control.

"We are encouraging all the nations in the region to take an active part in rebuilding the cease-fire so that we can return to the relative calm that was enjoyed in the region over the past six months," said state department spokesman Gordon Duguid.

He listed all the foreign leaders that Ms Rice had spoken to, from Tzipi Livni, her Israeli counterpart, to Saudi Foreign Minister Saud el-Faisal.

"We are working for a cease-fire now where Hamas must stop its rocket attacks on Israel," said Mr Duguid. "All sides then need to respect the ceasefire."

Bush failure

This is also in line with the approach taken by the Bush administration during its second term, according to Dan Senor, a former Bush administration official now working with the Council on Foreign Relations (CFR) - with the White House making strong statements in support of Israel while Condoleezza Rice leans a bit more strongly on Israel.

The flare-up also highlights the failure of Mr Bush to bring about a peace agreement between Palestinians and Israelis.

After he launched his ambition Annapolis peace initiative in 2007, few believed anything concrete would come out of it, but some argued that at least Mr Bush was leaving behind a work-in-progress, with relative calm on the ground.

Instead, the last few weeks of his presidency will be mired in yet another crisis - the biggest Israeli offensive against Gaza in decades.

While the escalation was pegged to a date - the end of a six-month cease-fire on 19 December - both the Israelis and Hamas seem to be using the political calendar in Israel and the US to reshuffle the cards before the next administration comes in.

Israeli officials know they can count on the Bush administration's support but are less sure about how an Obama administration would have reacted were they to have launched this operation after 20 January.

Mr Senor also argued that Israel did not want a flare-up in Gaza to be the first issue that Mr Obama would have to contend with when he moved into the White House.

"There was a sense in Israel that action was needed as the cease-fire was set to expire and they had to either move quickly or wait a long time - four or six months - and that was not something Israel could deal with," he said.

No details

But the developments are on such a scale that even if calm returns in a few days, the crisis will have an impact, possibly even regional, that will last beyond 20 January, so the Middle East is forcing itself high onto the agenda of the incoming administration.

Mr Obama has often said he would tackle the challenge of Middle East peace from day one, but has not given many details on how he plans to reach the peace deal that has eluded the Clinton and Bush administrations.

Israel's military operation in Gaza is also likely to limit his room for manoeuvre and diplomacy, at least in the beginning.

Mr Obama's team, stressing that there is only one president at a time, has kept its statements about the crisis to a minimum, but has provided assurances of its support for Israel.

"He's going to work closely with the Israelis," said David Axelrod, a senior advisor to Mr Obama. "They're a great ally of ours, the most important ally in the region."

"But he will do so in a way that will promote the cause of peace and work closely with the Israelis and the Palestinians on that, towards that objective," Mr Axelrod told the CBS Sunday talk show Face the Nation.

Steve Coll, a senior CFR fellow on Middle Eastern studies, said the Israelis were trying to do everything they could to get political cover from the incoming administration by highlighting statements by the president-elect, such as the one he made in August in Sderot, the Israeli town targeted by Hamas rocket attacks.

"If somebody was sending rockets into my house where my two daughters sleep at night, I'm going to do everything in my power to stop that," said Mr Obama during the visit. "And I would expect Israelis to do the same thing."

Gaza may well be that first international crisis that Vice President-elect Joe Biden predicted Mr Obama would have to face when he came into office, with both Israel and Hamas testing the incoming leader.

And while there is a good amount of good will awaiting Mr Obama in the Arab world, how he handles similar flare-ups during his presidency will determine how long the honeymoon lasts.