CRAWFORD, Texas (AP) — The deaths of hundreds of Palestinians in Israel’s deadliest-ever air assault on Hamas further complicate President-elect Barack Obama’s challenge to achieve a Middle East peace — something that eluded both the Bush and Clinton administrations.

The Bush administration has blamed the renewed violence on the militant Islamic group Hamas, which controls the Gaza Strip, saying it broke a cease-fire by firing rockets and mortars deep into Israeli territory. The Arab world, however, has reacted with rage to the aggressive Israeli counterattacks, which have left at least 290 Palestinians dead and more than 600 wounded.

It’s unclear whether Obama will be as supportive of Israel as President George W. Bush has been.

David Axelrod, senior adviser to Obama, chose his words carefully Sunday, saying the president-elect would honor the ‘‘important bond’’ between the United States and Israel.

‘‘He wants to be a constructive force in helping to bring about the peace and security that both the Israelis and the Palestinians want and deserve,’’ Axelrod said on CBS’ ‘‘Face the Nation.’’ ‘‘Obviously, this situation has become even more complicated in the last couple of days and weeks. As Hamas began its shelling, Israel responded. But it’s something that he’s committed to.’’

Pressed about how much support Obama will offer Israel, Axelrod said: ‘‘He’s going to work closely with the Israelis. 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 — toward that objective.’’

Israel had been carrying out its attack exclusively from the air, but the Israeli Cabinet has authorized the military to call up 6,500 reserve soldiers for a possible ground invasion.

‘‘I’m not sure it’s a good idea,’’ Sen. Sherrod Brown, D-Ohio, said Sunday on ABC’s ‘‘This Week.’’ ‘‘I mean, Israel certainly has the right to self-defense, of course. Hamas has not recognized Israel’s right to exist. … But I’m hopeful that as this transition comes, as we look to January, that strong presidential leadership can make a difference here.’’

Jon Alterman, head of the Middle East program at the Center for Strategic and International Studies in Washington, speculated that Israeli leaders synchronized their retaliatory attacks to political calendars in both Israel and the U.S. More moderate politicians running in the Feb. 10 national election needed to appear strong against Hamas, and it was perhaps better to strike before Bush left office on Jan. 20 because they weren’t as sure what Obama’s reaction would be.

‘‘I think Obama will be supportive of Israel, but will bring a little more skepticism to it,’’ Alterman said. ‘‘I think Obama will start from premise that Israel is an ally, but that we have to look at this fresh.’’

The White House was mum about the situation in Gaza on Sunday after speaking out strongly on Saturday. The Bush administration condemned the repeated rocket and mortar attacks against Israel and said it held Hamas responsible for breaking a cease-fire. The U.S. implored Israel to avoid civilian casualties and asked all concerned to address the urgent humanitarian needs of innocent people in Gaza.

Bush, who is staying at his Texas ranch, spoke on the phone with national security adviser Stephen Hadley to receive an update on the situation and was being kept abreast of developments throughout the day, said Gordon Johndroe, a presidential spokesman. He said Bush would receive an intelligence briefing via a secured video hookup at the ranch early Monday morning and would be briefed then on any overnight developments.

According to an aide on Obama’s transition team, the president-elect, who is in Hawaii, continues to closely monitor global events, including the situation in Gaza. He had an intelligence briefing Sunday and plans to talk with his incoming national security adviser, Gen. James Jones, and Sen. Hillary Rodham Clinton, his nominee for secretary of state.

The aide said Obama appreciates the information the Bush administration is sharing with him. The aide requested anonymity because the Obama team is refraining from comment, saying the U.S. has only one president at a time.

When Hamas took control of Gaza in June 2007, it fractured governance of the Palestinian territory. The other part, the West Bank, is controlled by moderate Palestinian President Mahmoud Abbas. The renewed violence increases the volatility of an already unstable area.

‘‘It undoubtedly will have a very severe impact on wherever the next administration would like to go,’’ Ed Abington, a former American diplomat who advises Abbas, said in an interview. ‘‘You can’t kill almost 300 Palestinians and wound 600 to 700 and not have repercussions in the region.’’

‘‘I don’t quite know where the Israelis want to end up,’’ he added, saying that trying to bomb Hamas into submission only rekindles radicalization. Abington said Israel’s retaliatory attacks weaken, not strengthen, the stature of Abbas, who is backed by the West.

Alterman said, however, that if Hamas is weakened by the bombings in Gaza, Abbas’ position could be emboldened. ‘‘It’s possible to imagine that he could emerge as some sort of broker who saves Gaza from an Israeli onslaught,’’ Alterman said.