Israel expects a "grave erosion" in its peace agreement with Egypt and is even preparing for the possibility of the historic deal collapsing altogether, a Cabinet minister said Wednesday, in the first official assessment of the unrest rocking Israel's southern neighbor.

The comments by Matan Vilnai, the minister for civil defense and a retired military general, reflected the government's grave concerns that Egypt's Muslim Brotherhood could make major gains and even win elections in Egypt that begin next week.

"The picture is quite clear. We've been saying it for months. Apparently what we call the Muslim Brotherhood ... will ultimately be the majority in all the (Egyptian) institutions," Vilnai told Israel's Army Radio station.

The Brotherhood is the most organized political group in Egypt and it is widely expected to make a strong showing in the election. Estimates of how much of parliament it will win have ranged from 20 percent to nearly 50 percent. Other Islamic fundamentalist parties are also running, raising the possibility that they could form a majority, though there are also divisions among the religious parties.

But amid Egypt's stormy politics, it is unclear how much leeway the Brotherhood will have after elections. It is under heavy pressure to work with liberal groups, and the military is likely to dominate the upcoming government.

Brotherhood leaders have said they do not seek to outright end the 1979 peace accord with Israel. Like many liberal and secular factions, they say they want amendments in the deal, particularly to change provisions that bar the Egyptian military from deploying in the Sinai Peninsula, near the border with Israel. Many in Egypt see that provision as a blow to national pride and as fueling insecurity in the desert territory.

Vilnai said he did not expect the peace agreement to unravel immediately since Egypt's post-revolution government will be preoccupied with domestic issues.

"But once the regime stabilizes, as we expect it to do, we expect that there will be a grave erosion of this agreement. And we have to prepare for such a situation," Vilnai said.

Israeli worries have been heightened by five days of mass protests in Cairo and other Egyptian cities demanding the ruling military immediately step aside and hand power to a civilian government. Nearly 40 people have been killed in clashes between security forces and protesters.

Egypt's military insists the violence will not prevent the beginning of parliamentary elections on Monday. The Brotherhood, eager to ensure that elections take place, has refused to join the new demonstrations, which have been led by liberal and secular activists.

Israel has favored the military's domination in Egypt, since the generals are a bulwark of support for the peace accord — not least because the army receives nearly $1 billion a year from the United States under the deal.

The peace agreement is a cornerstone of Israeli security. Israel's first with an Arab nation, it has kept a once-volatile border quiet for three decades and allowed the military to divert resources to deal with Palestinian militants in the West Bank and Gaza Strip, and Hezbollah guerrillas across Israel's northern border in Lebanon

Israeli security officials say they have been pleased with the Egyptian military's performance in stabilizing the country since President Hosni Mubarak was toppled in February.

Military officials say security coordination in the Sinai, which borders both Israel and the Hamas-ruled Gaza Strip, has returned to pre-revolution levels and fear that this could be disrupted after the Egyptian elections.

Israeli defense officials confirm the Israeli military has already begun preparing for a number of scenarios, including the possibility of the peace agreement being canceled. The officials spoke on condition of anonymity because they were discussing a sensitive security issue, and it was not clear whether the preparations are limited to discussions or include actual drills or troop deployments. The Israeli army did not immediately respond to a message seeking comment.

The army declined comment on any preparations it may be making. But it denied a report in an Israeli newspaper that the military chief, Lt. Gen. Benny Gantz, raised the possibility of peace collapsing in a briefing to top officials on Tuesday.

Zvi Marzel, Israel's former ambassador to Egypt, said he did not expect the Muslim Brotherhood to push the country to war with Israel. But he said the threat posed by the group should not be played down either.

He said the "heart of their ideology" is the destruction of Israel, and noted that the group is the parent of the violently anti-Israel Hamas militant group in Gaza.

He predicted the Brotherhood would be preoccupied with domestic issues after elections, and in any case, has said it would not contest the presidency, which holds must powers in Egypt.

"But they could back Hamas more, transfer weapons. They can definitely be more aggressive toward us and there could be crises and terror. But at this point, I don't think there will be war."