WASHINGTON — President-elect Barack Obama has promised that he will have plenty to say about the Israeli incursion into Gaza once he takes office next week, and expectations are high.

But there is a growing consensus among the people who have followed the Arab-Israeli conflict for decades that Mr. Obama must take some quick, decisive steps — within days of being sworn in — or else face the prospect of coming across in the Arab world as continuing President Bush’s tilt in favor of Israel.

During the two weeks of Israel’s bombardment of Gaza as reprisal for rockets launched from Gaza by Hamas, the militant Islamist group, Mr. Obama disappointed many commentators in the Muslim world by declining to condemn the Israeli operation.

“President-elect Obama is closely monitoring global events, including the situation in Gaza, but there is one president at a time,” said Mr. Obama’s national security spokeswoman, Brooke Anderson, repeating a mantra of the incoming administration.

Mr. Obama’s aides also pointed to statements Mr. Obama made during the campaign, in which he said he supported Israel’s right to defend itself from rocket attacks.

That stance has thus far been interpreted in the Arab world as a tacit assent to the Bush administration’s Middle East policy — the very policy that Mr. Obama criticized during the campaign as too divisive, and which he vowed to change.

Daniel Levy, a former Israeli peace negotiator, argues that by attacking Hamas in Gaza just days before the new administration takes over, Israeli leaders may have calculated that it is best to establish to the world, early and emphatically, that when the chips are down, Mr. Obama — and any American president — will stand by Israel over all others.

“There are some who argue that this forces Obama to side with us,” said Mr. Levy, director of the Prospects for Peace Initiative, a joint project of the New America Foundation and the Century Foundation. “In a way, that’s very brazen, this calculus that he might as well get himself washed in this from the start.”

For Mr. Obama, there are risks in being viewed in the Arab world as Bush 2.

“Polarization along the imagined Gaza fault lines traps the incoming Obama administration in an involuntary continuation of the Bush policies that contributed to the increased instability in the Middle East in the first place,” says Trita Parsi, author of Treacherous Alliance; The Secret Dealings of Israel, Iran and the U.S.”

If Mr. Obama wants to signal some shift from Mr. Bush’s position, there are a number of ways he can do it. First, Mr. Obama can call for an immediate ceasefire — if the hostilities are still raging on Jan. 20. The Bush administration abstained from the United Nations Security Council’s call last Thursday for an immediate ceasefire in Gaza that would lead to a withdrawal of Israeli troops, a resolution that was in any case rejected by Israel and ignored by Hamas.

Mr. Obama could also press Israel to open up the Gaza border crossings, and to lift the embargo that has left the territory in such dire straits. Many Israeli officials have already indicated that Israel would be amenable to a deal in which the Gaza crossings were opened with an international presence and a nominal Palestinian Authority presence — as long as it isn’t Hamas.

Mr. Obama could make a strong statement in support of a freeze of Israeli settlements in the West Bank, says Ghaith al-Omari, a former Palestinian peace negotiator. And finally, Mr. Obama could quickly start bullying, prodding and cajoling Israelis and Palestinians back to the negotiating table for comprehensive peace talks.

“He has to be more seriously engaged on the peace process,” said Mr. al-Omari, who is now advocacy director of the American Task Force on Palestine.

Speaking to George Stephanopoulos on ABC’s “This Week” on Jan. 10, Mr. Obama reiterated his promise that he will do something — and fast — concerning the seemingly never-ending Middle East conflict.

“The politics of it are hard,” he said, but “it’s so important for the United States to be engaged and involved immediately, not waiting until the end of their term.”