The dim prospect that U.S.-sponsored talks between Israelis and Palestinians could be resumed any time soon faded almost completely Tuesday after the bloody attack in a Jerusalem synagogue where five people, including three Americans, were killed by two Palestinian wielding knives and axes.

“The pace and intensity of violence are accelerating,” said Robert Danin, a former U.S. diplomat who is a senior fellow at the Council on Foreign Relations. “But it’s not at all clear there is a diplomatic means to stave it off. That’s what’s probably the hardest thing for American officials to get their heads around: What can you do, given how incendiary the environment there is?”

Jerusalem has witnessed a surge of violence in recent weeks, including a series of stabbings and vehicular attacks that killed six Israelis. But Tuesday’s attacks, in which rabbis at prayer and a policeman were killed, has deepened fears that tensions could spiral out of control.

“It’s like playing with matches at a gas station right now,” said Omar Kader, chairman of the Middle East Policy Council.

Alan Elsner, an official with J Street, which bills itself as a pro-Israel, pro-peace advocacy group, called the situation “dangerous, perilous.”

Two Palestinian men allegedly killed four people with axes and knives inside a synagogue in Jerusalem early Tuesday, before police shot them dead. The attack happened in an ultra-Orthodox neighborhood of West Jerusalem. (Reuters)

“I think the United States . . . should be urging calm and trying to stop the cycle of retribution and reprisal,” he said. “Because nobody wants to see this melt down as it looks like it might.”

In London, Secretary of State John F. Kerry spoke with evident anger as he condemned what he called “an act of pure terror and senseless brutality.” He said Palestinian leaders should “take serious steps to restrain any kind of incitement.”

Robert Satloff, executive director of the Washington Institute for Near East Policy, said that incident could doom the Obama administration’s efforts to get the parties back to the negotiating table in the near future.

“I do think today was uniquely shocking because of the vulnerability of the victims, the setting and the imagery of Jews praying in Jerusalem,” he said.

Since negotiations collapsed early this year, there has been no peace process that could be sabotaged by violence, said Haim Malka, deputy director of the Middle East program at the Center for Strategic and International Studies.

“What this does is further inflame both sides,” he said. “It leads to calls for revenge. And it deepens the cycle of violence. Which at some point could spark a much more intense wave of violence that would be difficult to stop.

“There’s a limit to what any administration can do. They can condemn violence. They can urge leaders to act calmly, and restrain calls for revenge. But the reality is they have a limited ability to change the violent dynamics on the ground.”

Danin said the incident is likely to propel Israelis and Palestinians further away from even considering talks, and the best the United States can do for now is serve as a buffer between the two camps.

“There are times in diplomacy when it’s better not to bring the parties together,” he said. “Just go back and forth between the parties, rather than get them together and have the situation deteriorate further. And right now, there’s not much receptivity for negotiations on either side, from either leader. Both sides feel victimized, and that’s a very bad place to be.”