The Israeli-Hamas conflict is putting the Obama administration at odds with two of its most important partners in the Middle East, threatening to undermine other U.S. objectives in the region at a time of political upheaval.

On Monday, Prime Minister Recep Tayyip Erdogan of Turkey, which has frequently served as a moderate voice in the region, described Israel as a “terrorist state” and condemned the airstrikes in the Gaza Strip, which is run by the Islamist group Hamas. Egyptian President Mohamed Morsi has warned Israel against a ground invasion and thrown his support behind Hamas’s leadership, sending his prime minister to Gaza.

The growing outcry has exposed the United States to criticism that it has not done enough to press Israel to agree to a cease-fire. The conflict has also created a wedge in relations with officials in Egypt and Turkey and highlighted the limits of U.S. influence in the aftermath of the revolutions that swept the region last year.

Against this backdrop, President Obama on Tuesday escalated U.S. involvement in trying to resolve the conflict, dispatching Secretary of State Hillary Rodham Clinton to meet with officials in Israel, the West Bank and Egypt. She leaves for the region from Phnom Penh, where she took part in the East Asia Summit with Obama.

Since the United States does not have relations with Hamas, however, Clinton is scheduled to meet in Ramallah with West Bank Palestinian leaders who are on the sidelines of the Gaza crisis, leaving it unclear how much she can hope to achieve.

Hours before Clinton was due to arrive in Israel, police and ambulances were called to the U.S. Embassy in Tel Aviv after a man attacked a guard, witnesses said.

Mickey Rosenfeld, a spokesman for the Israel Police said a 40-year-old Tel Aviv man armed with a knife and an ax attacked a guard at the U.S. embassy at approximately 11:30 a.m. The guard, who was “lightly injured,” fired “warning shots,” Rosenfeld said, but no one else was wounded.

Neither the new Islamist government in Egypt nor the established one in Turkey has succeeded in persuading Hamas to cease firing rockets from Gaza into Israel. Jordan — like Egypt, a traditional lever of U.S. influence in the Israeli-Palestinian conflict — has similarly been unable or unwilling to persuade Hamas militants to stand down.

An Egyptian official on Monday expressed frustration with the role played so far by the United States, which has made no attempt to publicly urge Israel to rein in its airstrikes.

The United States has the most sway with Israel of any “country on Earth,” said the official, speaking on the condition of anonymity to discuss the ongoing negotiations. “The Israelis would not listen easily to any other voice.”

The Obama administration has pleaded for all sides to “de­escalate” but has criticized only Hamas. Ahead of Clinton’s visit to the region, all high-level U.S. diplomacy has been conducted from afar, including phone calls Monday from Obama to Morsi and to Israeli Prime Minister Benjamin Netanyahu.

International diplomatic efforts for a cease-fire intensified in Cairo, but the United States did not expressly back any plan.

“We don’t practice diplomacy from the podium,” State Department spokeswoman Victoria Nuland said Monday. “We have been very clear that Israel has a right of self-defense. We’ve been very clear that rockets continue to be fired and land on Israel. We’ve been very clear that we are working to try to get this conflict de­escalated. We have been very clear about our concern for the civilians and innocents on both sides who are getting caught in this.”

The administration, meanwhile, has tried to tread carefully with Egypt and Turkey. It is seeking to recalibrate relations with the former in the wake of the election of an Islamist leader, while relying on the latter as its main diplomatic bulwark against further deterioration of the situation in Syria.

U.S. officials have supported both countries as possible peacemakers in Gaza but abstained from criticism of their embrace of Hamas.

“Our position continues to be that those nations in the region, particularly nations that have influence over Hamas, and that’s principally Egypt and Turkey, also Qatar . . . that those nations need to use that influence to ­de-escalate the conflict,” White House deputy national security adviser Ben Rhodes said Monday. “De-escalation has to begin with, again, an end to rocket fire from Gaza.”

The difficult diplomatic position for the United States recalled the Israeli war with Lebanon in 2006, when European and Arab nations lobbied the George W. Bush administration to intercede with Israel or to push for a cease-fire. The United States at first resisted calls for a cease-fire, because Israel argued that it needed the military latitude.

Diplomatic efforts this time are complicated by relations between two U.S. allies in the region, Israel and Turkey.

Ties between the two crumbled in 2010 after Israeli marines stormed an aid ship to enforce a naval blockade of the Gaza Strip. Nine Turks were killed in clashes with activists on board.

Ankara expelled Israel’s ambassador and froze military cooperation when a U.N. report released last year largely exonerated the Jewish state in the incident. This month, Turkey opened the trial in absentia of four former Israeli military commanders over the 2010 raid.

Turkish Foreign Minister Ahmet Davutoglu is to travel to Gaza on Tuesday with a group of foreign ministers from the Arab League.

The diplomatic stalemate is also playing out at the United Nations.

On Monday, the U.N. Security Council began deliberations on a statement introduced by Morocco, the council’s only Arab member, calling for an immediate halt to “all military activities” in Gaza. A Security Council diplomat said that 14 of the council’s 15 members “pronounced themselves in favor” of starting negotiations on the draft.

The United States, however, said it was “not in a position to engage,” said the diplomat, who spoke about the closed-door discussions on the condition of anonymity. U.N. Ambassador Susan E. Rice argued that the United States had concerns that a hasty move in the council to weigh in on the matter might jeopardize cease-fire negotiations underway in the region.

After the meeting, Russia’s U.N. envoy, Vitaly Churkin, expressed frustration with the council’s failure to act. “We are upset that the draft press statement which was circulated by Morocco on behalf of the Arab League as early as Thursday night is still bogged down in discussion,” he said.

Colum Lynch at the United Nations and Michael Birnbaum in Cairo contributed to this report.