Will Israel-Hamas cease-fire hold?

• Hamas rivals might continue to attack Israel
• Improving Gaza economy could be key
• Israel wants to keep weapons out of Gaza

Any cease-fire agreement that requires Hamas to stop rocket fire from Gaza into Israel will be tenuous because rival militant groups will try to shatter it, Middle East analysts say.

Palestinian groups such as Islamic Jihad, the Popular Resistance Committee and others "are Iranian sponsored and will undoubtedly try to scuttle this" by firing rockets into Israel, says Jonathan Schanzer, a former terror financing analyst at the Treasury Department and now vice president of research at the Foundation for the Defense of Democracies, a Washington think-tank.

Like Hamas, they are armed by Iran, whose relations with Hamas have worsened in recent months after Hamas broke with Iran over its support of Syrian President Bashar Assad.

Though Iran "will have a major stake" in trying to get Hamas' rivals to disrupt the deal, Hamas will have to reign in those smaller groups, says Aaron David Miller, vice president of the Woodrow Wilson Center, a Washington think-tank.

"I don't think Hamas would have gone into this agreement if they weren't capable of enforcing it," Miller says.

Though the details are unclear, the agreement is likely to include a sweetener, such as opening up the border with Egypt, which would make Hamas "literally the new king of Gaza," Miller says. If the opening is meaningful, Hamas "will have significant leverage over these smaller groups," he says.

In Gaza, "Hamas' capacity to assert control will be directly related to how the deal improves lives for Palestinians," Miller says.

Israel is likely to require safeguards to make sure an opening of Egypt's border with Gaza does not result in a flood of weapons into the territory, Miller says.

Though Hamas may control what happens in Gaza, it will not be expected to control what happens across its southern border in the Egyptian-controlled Sinai Peninsula where jihadi groups have grown in influence since the Arab Spring uprising that deposed Egyptian President Hosni Mubarak in 2011.

Israel is likely to understand Hamas' limitations in the peninsula, Miller says.

The terms of the cease-fire almost all hinge on Egypt, Schanzer says.

Egypt will bear responsibility for preventing additional Iranian rockets from entering Gaza and for policing what comes out of Gaza to the Sinai that could threaten Egyptian and Israeli security, Schanzer says.

On the one hand, it looks like the United States prevailed upon Egypt to revert to its role under Mubarak to enforce calm in the region, Schanzer says.

On the other hand, Hamas obtained more than 100 long-range rockets from Iran via Sudan under Egypt's watch, and "it remains a question whether Egypt was complicit or caught off guard" in that endeavor, he says.

Though Hamas may not be willing to sit down and negotiate peace with Israel, it may agree to enforce a calm as part of an economic package that Egyptian and Hamas leaders have discussed for months, Schanzer says.

They've talked about closing the underground tunnels Hamas uses to supply Gazans with goods from Egypt and to procure weapons. Also under discussion is the idea of bringing Gaza's economy into the open with a free-trade zone in Egypt, he says.

Despite its charter that calls for the destruction of Israel, "Hamas doesn't think for a minute they're going to destroy Israel," Schanzer says. "But people are listening, and this is their demand. They want to open up Gaza, and they're counting on Egypt to do it."